z = x + y – 1

Private Sub cmdAddSheets_Click()
'dim variables
Dim x As Integer
Dim y As Integer
Dim z As Integer
'set error handler
On Error GoTo Copier_Error
'turn off screen updating and calculation
Application.ScreenUpdating = False
Application.Calculation = xlCalculationManual
'check if the workbook isshared and exit if it is
If ThisWorkbook.MultiUserEditing Then
MsgBox "Please Unshare the workbook before you proceed"
Exit Sub
End If
'check that all values are in the userform
If Me.txtName = "" Or Me.cboNum = "" Or Me.cboNumSt = "" Then
MsgBox "You forgot to add the parematers for the sheet name."
Exit Sub
End If
'protect_all
Protect_All
'set variables for number of sheet
x = Me.cboNum.Value
'set variable for sheet name prefix
y = Me.cboNumSt.Value
z = x + y – 1
'check the first sheet name
NewName = Sheet1.Range("A4")
'loop through to check
For Each sh In ThisWorkbook.Worksheets
If sh.Name = NewName Then
MsgBox "This information already exists.You are not permitted to copy over it"
'if sheet name exists then got to end of sub
GoTo Copier_Error:
End If
Next
'run loop to add sheets
For numtimes = y To z
Sheet3.Copy after:=Worksheets(Worksheets.Count)
'create the new sheet name
ActiveSheet.Name = Me.txtName & numtimes
Next
'return to Interface sheet
Sheet1.Select
'list workshhet names on the interface
ListWorkSheetNames
'turn of screen updating and calculation
Application.ScreenUpdating = True
Application.Calculation = xlCalculationAutomatic
'error handler
On Error GoTo 0
Exit Sub
Copier_Error:
'message if sheet already exists
MsgBox "I think " & NewName & " already exists.  Check the starting number"
End Sub