This code checks if a specific worksheet is hidden in the workbook.
VBA Code:
Function IsWorksheetHidden(ByVal worksheetName As String) As Boolean
Dim ws As Worksheet
On Error Resume Next
Set ws = Worksheets(worksheetName)
On Error GoTo 0
If Not ws Is Nothing Then
IsWorksheetHidden = ws.Visible = xlSheetHidden
Else
IsWorksheetHidden = False
End If
End Function