How to call another function within a function in VBA - excel

Question

I'm currently trying to detect duplicated sheet name using "CheckSheet" function. And I want to call this function to run in "Add Sheet" to prevent users from creating duplicate sheet names. However, I ran into error "Compile Error: Expected function or variable" and still not succeeding in solving the problem. Kindly enlighten me where I am doing it wrong and feel free to point out if there are any weakness and better optimization to my code. Thanks in advance.
Option Explicit
Public sheetName As Variant
Public cS As Variant
Sub CheckSheet(cS) 'To check duplicate sheet name - used in AddSheet function.
Dim wS As Worksheet
Dim wsName As String
wsName = wS(sheetName)
On Error GoTo 0
If wS Is Nothing Then
cS = False
Exit Sub
End Sub
Sub AddSheet()
Dim cSheet As Variant
cSheet = CheckSheet(cS).Value
On Error Resume Next
sheetName = Application.InputBox(prompt:="New Sheet Name", Left:=(Application.Width / 2), Top:=(Application.Height / 2), Title:="Add Sheet", Type:=2)
If sheetName = "" Then
MsgBox "Sheet name cannot be empty!"
Exit Sub
ElseIf cSheet = False Then
MsgBox "Duplicate Name! Please try again!"
Exit Sub
Else
Application.ScreenUpdating = False
Sheets.Add(After:=Sheets(Sheets.Count)).Name = sheetName
MsgBox """" & sheetName & """ was successfully created!"
Sheets("Sheet1").Activate
End If
End Sub

Answer 1

Two things.
1. Your code can be simplified. You do not need a function to check if a worksheet exists.
Option Explicit
Sub AddSheet()
Dim sh As Object
Dim sheetName As Variant
'~~> Accept user input
sheetName = Application.InputBox(prompt:="New Sheet Name", _
Left:=(Application.Width / 2), _
Top:=(Application.Height / 2), _
Title:="Add Sheet", Type:=2)
'~~> User presses cancel
If sheetName = False Then Exit Sub
'~~> Check if the sheet name is empty
If sheetName = "" Then
MsgBox "Sheet name cannot be empty!"
Exit Sub
End If
'~~> Check if the sheet exists
On Error Resume Next
Set sh = ThisWorkbook.Sheets(sheetName)
On Error GoTo 0
If Not sh Is Nothing Then
MsgBox "Duplicate Name! Please try again!"
Exit Sub
End If
'~~> Create the worksheet
With ThisWorkbook
.Sheets.Add(After:=.Sheets(.Sheets.Count)).Name = sheetName
MsgBox """" & sheetName & """ was successfully created!"
End With
End Sub
2. Even if you want to use a function, your code has lot of errors. (One of them is pointed out by #braX above.
Is this what you are trying?
Option Explicit
Sub AddSheet()
Dim sheetName As Variant
'~~> Accept user input
sheetName = Application.InputBox(prompt:="New Sheet Name", _
Left:=(Application.Width / 2), _
Top:=(Application.Height / 2), _
Title:="Add Sheet", Type:=2)
'~~> User presses cancel
If sheetName = False Then Exit Sub
'~~> Check if the sheet name is empty
If sheetName = "" Then
MsgBox "Sheet name cannot be empty!"
Exit Sub
End If
'~~> Check if the sheet exists
If DoesSheetExists(CStr(sheetName)) = True Then
MsgBox "Duplicate Name! Please try again!"
Exit Sub
End If
'~~> Create the worksheet
With ThisWorkbook
.Sheets.Add(After:=.Sheets(.Sheets.Count)).Name = sheetName
MsgBox """" & sheetName & """ was successfully created!"
End With
End Sub
'~~> Function to check if sheet exists
Private Function DoesSheetExists(wsName As String) As Boolean
Dim sh As Object
'~~> Check if the sheet exists
On Error Resume Next
Set sh = ThisWorkbook.Sheets(wsName)
On Error GoTo 0
If Not sh Is Nothing Then DoesSheetExists = True
End Function