I stole this from Chip Pearson:
Function WorksheetExists(SheetName As Variant, _
Optional WhichBook As Workbook) As Boolean
'from Chip Pearson
Dim WB As Workbook
Set WB = IIf(WhichBook Is Nothing, ThisWorkbook, WhichBook)
On Error Resume Next
WorksheetExists = CBool(Len(WB.Worksheets(SheetName).Name) > 0)
End Function
'and you can use it like:
....
if worksheetexists("myname",activeworkbook) then