AH and AL are not valid range assignments
AH:AH and AL:AL are valid
Lose the spaces, except around the Ampersands
I'm not sure, but try
DAdd = Application.WorksheetFunction.SumIfs(Sheet1!AL:AL, Sheet1!AH:AH,">=" & DateRangeStart, Sheet1!AH:AH."<=" & DaterangeEnd)
Those Ranges might not work because a blank cell is less than DateRangeEnd
See what this does
Sub ADDITUP()
Dim DAdd As Variant
Dim DateRangeStart as Date
Dim DateRangeEnd As Date
Dim SumRange As Range
Dim CritRange As Range
With Sheets("Sheet1")
'AL1 with no headers. Use AL2 with headers
Set SumRange = Range(.Range("AL1"), .Cells(Rows.Count, "AL").End(xlUp))
Set CritRange = SumRange.Offset(0, -4)
End With
'The Returns from InputBoxes are Strings.
'Specifying the Month eliminates International Date Format confusion
'Format the converted Dates from the inputBoxes as desired
DateRangeStart = Format(CDate(InputBox("Please select start date (01 Jan, 2018)")), "dd/mm/yyyy")
DateRangeEnd = Format(CDate(InputBox("Please select end date (Jan 31, 2018)") "dd/mm/yyyy")
DAdd = Application.WorksheetFunction.SumIfs(SumRange, CritRange, ">=" & DateRangeStart, CritRange, "<=" & DaterangeEnd)
'MsgBox DAdd
'MsgBox DateRangeStart
'MsgBox DaterangeEnd
End Sub
Note: if Column AH is formatted As Dates of any display format, you should not need to Format DateRangeStart and DateRangeEnd, only CDate the InputBoxes returns.