Thanks to all that have helped and for all those that have tried.
I have now found the answer, may it help others.
Sub ABC()
Dim sh As Object, sh1 As Object
Dim sh2 As Object, Sh3 As Object
Dim ar As Range, s1 As String
Dim s As String, s2 As String
Dim i As Long, rng As Range
Dim v() As Object
ReDim v(1 To 6)
s2 = "B6:E24,G6:H24,K6:P24,B28:E49,G28:H49,K28:P49"
i = 0
For Each sh In ActiveWorkbook.Sheets
Select Case Left(sh.Name, 3)
Case "Sat", "Mon", "Tue", "Wed", "Thu", "Fri"
If sh1 Is Nothing Then
Set sh1 = sh
End If
Set sh2 = sh
Case "WEE"
If Not sh1 Is Nothing Then
s = "'" & sh1.Name & ":" & sh2.Name & "'!"
Set rng = sh.Range(s2)
For Each ar In rng.Areas
ar.Formula = "=Sum(" & s & _
ar(1).Address(0, 0, xlA1) & ")"
Next
End If
i = i + 1
Set v(i) = sh
Set sh1 = Nothing
Set sh2 = Nothing
Case Else
If InStr(1, sh.Name, "MONTH", vbTextCompare) Then
Set Sh3 = sh
Set sh1 = Nothing
Set sh2 = Nothing
End If
End Select
Next
If Not Sh3 Is Nothing Then
s = ""
For i = LBound(v) To UBound(v)
On Error Resume Next
Set sh = v(i)
On Error GoTo 0
If Not sh Is Nothing Then
s = s & "'" & sh.Name & "'!ZZZ,"
End If
Next
s = Left(s, Len(s) - 1)
Set rng = Sh3.Range(s2)
For Each ar In rng.Areas
s1 = Replace(s, "ZZZ", ar(1).Address(0, 0))
ar.Formula = "=Sum(" & s1 & ")"
Next
Else
MsgBox "No Monthly Sheet found"
End If
End Sub
Nurofen