Problem

If cmdNought(SquareNumber).Caption <> "" Then
MsgBox "Square already taken"

Option Explicit
Dim Player1 As Boolean
Dim Name1 As String
Dim Name2 As String






Private Sub cmdNought_Click(Index As Integer)
'Declare required storage
    picOutput.Cls

 
    Call PlaceSymbol(Index)
   
   If Player1 Then
   picOutput.Print "Player two to go "
   Else
   picOutput.Print "Player one to go "
   End If
  
  
End Sub

Private Sub cmdPlay_Click()
'Declare required storage
Dim Name1 As String
Dim Name2 As String

Do

'Require user to input their name
    Name1 = InputBox("Please enter your name ", "Enter Name")

    Name1 = UCase(Left(Name1, 1)) & LCase(Right(Name1, Len(Name1) - 1))
'Output player one's name
Loop Until Name1 > ""
    picOutput.Print "Player one is "; ""; (Name1)
    
    
Do
Name2 = InputBox("Please enter your name ", "Enter Name")
    Name2 = UCase(Left(Name2, 1)) & LCase(Right(Name2, Len(Name2) - 1))
Loop Until Name2 > ""
'Output player two's name
    picOutput.Cls
    picOutput.Print "Player two is  "; ""; (Name2)
    
    picOutput.Print "Player one "; (Name1); " to go first "
    
End Sub

Private Sub cmdQuit_Click()
' Terminate Application
    End
End Sub

Private Sub cmdSquare_Click(Index As Integer)

Call PlaceSymbol(Index)

End Sub
Private Sub PlaceSymbol(SquareNumber As Integer)


  
  
  'carry out players actions
  
   If cmdNought(SquareNumber).Caption <> "" Then
   MsgBox "Square already taken"
  End If
  
  If Player1 Then
    cmdNought(SquareNumber).Caption = "O"
  Else
  
    cmdNought(SquareNumber).Caption = "X"
  End If
  
   

  Player1 = Not Player1

   
End Sub