Why VBA sometimes reconized the next variable (x1Whole) and sometimes not - excel

Question

I have a first version of the next code in VBA for excel
Function findCell(celda As String, rnc As String) As String
Dim cell As Range
Dim pos As String
Range("A2").Select
Set cell = Cells.Find(What:=celda, After:=ActiveCell, LookIn:= _
xlFormulas, LookAt:=xlPart, SearchOrder:=xlByRows, SearchDirection:= _
xlNext, MatchCase:=False, SearchFormat:=False)
If cell Is Nothing Then
pos = 0
Else
pos = cell.row
End If
findCell = pos
End Function
The function recive a string and return the position in number of the column, but After I change a parameter because I must be find the full contain of the cell. And I change the value lookAt from x1Part to x1Whole
Set cell = Cells.Find(What:=celda, After:=ActiveCell, LookIn:= _
xlFormulas, LookAt:=xlWhole, SearchOrder:=xlByRows, SearchDirection:= _
xlNext, MatchCase:=False, SearchFormat:=False)
When I try to run the macro doesnt work sometimes and show me that value x1Whole, but when I run from the editor works.

Answer 1

If you seek a string in a formula as xlPart, you always get the string from your function itself (a good idea, btw). There will be a problem with xlWhole: there may be a case (and if the formula is the only thing in the sheet, it is is the case) that there's no match. Find will give an error, if nothing is found, and the formula result will be #N/A.
Below is your code with error handling, resulting in 0 for no match.
Function findCell(celda As String, rnc As String) As String
Dim cell As Range
Dim pos As String
On Error GoTo Nomatch
Set cell = Cells.Find(What:=celda, After:=Range("A2"), LookIn:= _
xlFormulas, LookAt:=xlWhole, SearchOrder:=xlByRows, SearchDirection:= _
xlNext, MatchCase:=False, SearchFormat:=False)
Nomatch:
If cell Is Nothing Then
pos = 0
Else
pos = cell.Row
End If
findCell = pos
End Function
Also, I removed Select("A2"), and moved it to After:=Range("A2").