Slightly changed to David Murdoch's code for generic library
Function HasByName(cSheetName As String, _
Optional oWorkBook As Excel.Workbook) As Boolean
HasByName = False
Dim wb
If oWorkBook Is Nothing Then
Set oWorkBook = ThisWorkbook
End If
For Each wb In oWorkBook.Worksheets
If wb.Name = cSheetName Then
HasByName = True
Exit Function
End If
Next wb
End Function