'------------------------------------------------
Sub CreateSummary()
     '
     ' Macro to create summary table containing the _
    Min, Max, And 3 Quartiles of each sheet In _
    the workbook. The user Is requested To _
    Input the first cell of the range For the _
    calculations. In addition the value of the _
    row at 'Z' (in column C) is entered in the _
    table.
     '------------------------------------------------
    Dim rInp As Range, rOut As Range, rFnd As Range, rSrch As Range
    Dim wsIn As Worksheet, wsSum As Worksheet
    Dim lR As Long
    Dim vOut As Variant
    Const sZZZ As String = "Z" ' This is the value to indicate special row
    Const iCCC As Integer = 3 'Column C where sZZZ is to be searched
     
     ' Check if Summary sheet exists, else create
    On Error Resume Next 'in case it doesn't exist
    Set wsSum = Sheets("Summary")
    On Error GoTo 0 ' reset error behaviour
    If wsSum Is Nothing Then ' sheet does not exist
        Set wsSum = Sheets.Add(after:=Sheets(Sheets.Count))
        wsSum.Name = "Summary"
    End If
    Set rOut = wsSum.Range("D2")
     
     'for our output we will gather the data into an array _
    Then print out a row at once For Each sheet. _
first the header:
    ReDim vOut(1 To 1, 1 To 7)
    vOut(1, 2) = "Z"
    vOut(1, 3) = "Min"
    vOut(1, 4) = "Q1"
    vOut(1, 5) = "Q2"
    vOut(1, 6) = "Q3"
    vOut(1, 7) = "Max"
    rOut.Resize(1, 7).Value = vOut 'print headers to sheet
    Set rOut = rOut.Offset(1, 0) ' set to next row
     
     ' Now go through each sheet, get user to enter _
    range For processing. Then calculate quartiles _
    And add the Z figure.
     
    For Each wsIn In Sheets
        If wsIn.Name <> wsSum.Name Then
GetRange:
            wsIn.Activate
            On Error GoTo CleanUp
            Set rInp = Application.InputBox( _
            prompt:="Please select 1st cell of range in this sheet " _
            & vbCrLf & "to be processed for Quartiles (to use the whole column)" & vbCrLf _
            & "Or select the ranges individually using mouse and Ctrl key." & vbCrLf _
            & "You can use your mouse to select", _
            Title:="Select Quartiles Range", _
            Type:=8)
            On Error GoTo 0
            If rInp Is Nothing Then GoTo GetRange ' loop if invalid input
            If rInp.Parent.Name <> wsIn.Name _
            Then GoTo GetRange ' loop if multiple columns selected or on wrong sheet
             
            If rInp.Cells.Count = 1 Then
                 ' extend range to end of sheet
                lR = wsIn.Cells(Rows.Count, rInp.Column).End(xlUp).Row '  last row, now skip summary if exists
                If wsIn.Cells(lR, rInp.Column).Offset(-1, 0) = vbNullString Then ' there is a summary line,
                    lR = wsIn.Cells(lR, rInp.Column).End(xlUp).Row 'exclude it
                End If
                Set rInp = rInp.Cells(1, 1).Resize(lR - rInp.Row + 1, 1)
            End If
             ' calculate quartiles from provided range
            With Application.WorksheetFunction
                vOut(1, 1) = wsIn.Name
                vOut(1, 3) = .Min(rInp)
                vOut(1, 4) = .Quartile(rInp, 1)
                vOut(1, 5) = .Quartile(rInp, 2)
                vOut(1, 6) = .Quartile(rInp, 3)
                vOut(1, 7) = .Max(rInp)
            End With
             'find the 'Z'
            Set rSrch = wsIn.Cells
            Set rFnd = rSrch.Find(what:=sZZZ, after:=Cells(rInp.Row - 1, 3), _
            lookat:=xlWhole, LookIn:=xlValues, _
            searchdirection:=xlNext)
            If rFnd Is Nothing Then ' not found
                vOut(1, 2) = vbNullString
            Else ' get value at intersection of column and row
                vOut(1, 2) = Intersect(rInp, wsIn.Rows(rFnd.Row)).Value
            End If
            rOut.Resize(1, 7).Value = vOut 'print values to sheet
            Set rOut = rOut.Offset(1, 0) ' set to next row
             
        End If
    Next wsIn
     
     'format table
    Set rOut = rOut.Offset(-1, 0).CurrentRegion
    FormatSumTbl rOut
    wsSum.Activate
     
CleanUp:
    Set wsIn = Nothing
    Set wsSum = Nothing
    Set rOut = Nothing
    Set rInp = Nothing
    Set rFnd = Nothing
    Set rSrch = Nothing
     
End Sub
 
 
 
 
Sub FormatSumTbl(rTbl As Range)
     '
     ' FormatSumTbl Macro
     ' Format the Summary Table & headings
     '
     
     
     '
    With rTbl
        .HorizontalAlignment = xlCenter
        .NumberFormat = "0.0"
        .Borders(xlDiagonalDown).LineStyle = xlNone
        .Borders(xlDiagonalUp).LineStyle = xlNone
        With .Borders(xlEdgeLeft)
            .LineStyle = xlContinuous
            .ColorIndex = 0
            .TintAndShade = 0
            .Weight = xlMedium
        End With
        With .Borders(xlEdgeTop)
            .LineStyle = xlContinuous
            .ColorIndex = 0
            .TintAndShade = 0
            .Weight = xlMedium
        End With
        With .Borders(xlEdgeBottom)
            .LineStyle = xlContinuous
            .ColorIndex = 0
            .TintAndShade = 0
            .Weight = xlMedium
        End With
        With .Borders(xlEdgeRight)
            .LineStyle = xlContinuous
            .ColorIndex = 0
            .TintAndShade = 0
            .Weight = xlMedium
        End With
        With .Borders(xlInsideVertical)
            .LineStyle = xlContinuous
            .ColorIndex = 0
            .TintAndShade = 0
            .Weight = xlThin
        End With
        With .Borders(xlInsideHorizontal)
            .LineStyle = xlContinuous
            .ColorIndex = 0
            .TintAndShade = 0
            .Weight = xlThin
        End With
        With .Columns(1)
            .Borders(xlInsideHorizontal).LineStyle = xlNone
            .EntireColumn.AutoFit
            With .Font
                .Color = -16776961
                .TintAndShade = 0
            End With
        End With
        With .Rows(1)
            .Font.Underline = xlUnderlineStyleSingle
        End With
        With .Columns(2)
            .Font.Bold = True
            .Font.Underline = xlNone
        End With
        With Cells(1, 2).Font
            .Color = -16776961
            .TintAndShade = 0
        End With
    End With
End Sub
try this. It allows the user to select non contiguous ranges . If (s)he selects one cell then the column is used if selecting sepearate ranges (using the mouse & ctrl key) then those ranges are used. So cells T5:T89, W90:W95, T96:T107 can be selected (all at the same time).

It still automatically goes to the next sheet. Will that be sufficient?