Function results incorrectly applied to multiple worksheets

Thanks Rory
Adjusted the code.

Function PT_Site_Name(Cell As Range)
    Dim r As Range
    With Cell.Worksheet
        Set r = .Range(.Cells(1, Cell.Column), .Cells(Cell.Row, Cell.Column)).Find("*", SearchOrder:=xlByRows, SearchDirection:=xlPrevious)
    End With
    PT_Site_Name = r.Value
End Function