I have an Excel workbook with numerous sheets entitled "Week1", "Week2", "Week3" ... "Week7". Each week, I input the customers IDs of people buying my product in column C, and -- as I am interested knowing if these are return customers or if they are new ones -- I have written a function to check if the customers I input in Week2-Week7 are new customers or whether they have previously bought my product.

To that end, I have developed the following formula which I input into column F for Week2:

```
=IF(COUNTIF(Week1!$C$3:$C$100,C3)>=1,"Old","New")
```

With the relevant part of "Week1" looking like:

```
_|-----C-----|-----F-----|
3| ValPot1 | *blank* |
```

With the relevant part of "Week2" looking like:

```
_|-----C-----|-----F-----|
3| ValPot1 | Old |
```

Now, although this works well, it becomes rather cumbersome by the Week7, when I have to use the following function:

=IF(OR(COUNTIF(Week1!$C$3:$C$100,C3)>=1,COUNTIF(Week2!$C$3:$C$100,C3)>=1,COUNTIF(Week3!$C$3:$C$100,C3)>=1,COUNTIF(Week4!$C$3:$C$10>0,C3)>=1,COUNTIF(Week5!$C$3:$C$100,C3)>=1,COUNTIF(Week6!$C$3:$C$100,C3)>=1),"Old","New")

Consequently, I've been trying (unsuccessfully) to use the following VBA function:

```
Function SHEETOFFSET(offset, Ref)
' Returns cell contents at Ref, in sheet offset
Application.Volatile
With Application.Caller.Parent
SHEETOFFSET = .Parent.Sheets(.Index + offset) _
.Range(Ref.Address).Value
End With
End Function
```

By incorporating it in sheet "Week2", cell `F3`

, in the following manner:

```
=IF(COUNTIF(SHEETOFFSET(-1,$C$3):SHEETOFFSET(-1,$C$100),C3)>=1,"Old","New")
```

In effect, I'm just replacing my previous worksheet reference (of `Week1!$C$3:$C$100`

) with my new `SHEETOFFSET`

function....

Unfortunately, this doesn't work, and simply returns a `#VALUE!`

error. What am I doing wrong, and how can I fix my function?