Excel's Formula - sisman

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Part VI: Developing Custom Worksheet Functions
If Wksht.Range(Addr) > MaxVal Then _
MaxVal = Wksht.Range(Addr).Value
End If
End If
Next Wksht
If MaxVal = –9.9E+307 Then MaxVal = CVErr(xlErrValue)
MAXALLSHEETS = MaxVal
End Function
The For Each statement uses the following expression to access the workbook:
cell.Parent.Parent.Worksheets
The parent of the cell is a worksheet, and the parent of the worksheet is the workbook. Therefore,
the For Each-Next loop cycles among all worksheets in the workbook. The first If statement
inside the loop checks whether the cell being checked is the cell that contains the function. If so,
that cell is ignored to avoid a circular reference error.
You can easily modify the MAXALLSHEETS function to perform other cross-worksheet
calculations: Minimum, Average, Sum, and so on.
The SHEETOFFSET function
A recurring complaint about Excel (including Excel 2010) is its poor support for relative sheet
references. For example, suppose that you have a multisheet workbook, and you enter a formula
like the following on Sheet2:
=Sheet1!A1+1
This formula works fine. However, if you copy the formula to the next sheet (Sheet3), the formula
continues to refer to Sheet1. Or if you insert a sheet between Sheet1 and Sheet2, the formula continues
to refer to Sheet1, when most likely, you want it to refer to the newly inserted sheet. In
fact, you can’t create formulas that refer to worksheets in a relative manner. However, you can
use the SHEETOFFSET function to overcome this limitation.
Following is a VBA Function procedure named SHEETOFFSET:
Function SHEETOFFSET(Offset As Long, Optional cell As Variant)
‘ Returns cell contents at Ref, in sheet offset
Dim WksIndex As Long, WksNum As Long
Dim wks As Worksheet
Application.Volatile
If IsMissing(cell) Then Set cell = Application.Caller