CheckBox(n).enabled = false

Function listExist() As Boolean
Dim strName As String
Dim i, k As Integer
For i =  1  To  12 
    For k =  9  To  10 
    strName = "0" + CStr(i) + ";0" + Cstr(k)
    On Error Resume Next
    listExist = WorkSheets(strName).Index
    Next k
Next i        
End Function

 strName = "0" + CStr(i) + ";0" + Cstr(k)

Public Sub CheckWrkSh()
Dim i As Integer
Dim k As Integer
    
    For i =  1  To  24 
      UserForm1.Controls("CheckBox" + CStr(i)).Enabled = SheetIndex(((i -  1 ) \  12 ) +  9 , ((i -  1 ) Mod  12 ) +  1 ) <> - 1 
    Next i

End Sub




Function SheetIndex(iYear As Integer, iMonth As Integer) As Integer
SheetIndex = - 1 
On Error Resume Next
SheetIndex = Worksheets(Format(CStr(iMonth),  0 ) + "," + Format(CStr(iYear),  0 )).Index
End Function

Format(CStr(iMonth),  0 ) 

SheetIndex = Worksheets(Format(iMonth, MM) + "," + Format(iYear,  0 )).Index

Function PadL(pstr As String, pcnt As Long, ch As String)
  Dim strTmp As String
  strTmp = pstr
 Do While Len(strTmp) < pcnt
  strTmp = ch + strTmp
 Loop
 PadL = strTmp
End Function

Function SheetIndex(iYear As Integer, iMonth As Integer) As Integer
    SheetIndex = - 1 
    On Error Resume Next
       SheetIndex = Worksheets(PadL(CStr(iMonth),  2 , "0") + "," + Right(CStr(iYear),  2 )).Index
End Function

Format$(iMonth,"00")

Right(imonth+ 100 ,  2 )