The following User Defined Function is referencing previous excel sheet.
Function PrevSheet()
Application.Volatile
PrevSheet = Worksheets(ActiveSheet.Index - 1).Name
End Function
The following formula is okey.
=Sheet1!A1
The following formula is NOT okey. The following formula needs to repaired.
=PrevSheet()!A1
Expansion on my comment to do this all in a UDF:
Function PrevSheetVal(PrevSheetRow As Long, PrevSheetCol As Long) As String
Application.Volatile
PrevSheetVal = Worksheets(ActiveSheet.Index - 1).Cells(PrevSheetRow, PrevSheetCol).Value
End Function
Used like:
=PrevSheetVal(1,1)
Which will return the value in cell A1
of the "Previous sheet" as defined by the sheet with an index 1 less than the Activesheet