Open userform in powerpoint from excel

[Jhon90]

Sir,
I have an Userform in PowerPoint say Userform1. Now I want to open this userform1 from excel sheet(command button). But below code is not working.
NOTE: Frist I opened PowerPoint & then pressed command button in excel.

Sub showUserForm()
Dim PowerPointApp As Object
Set PowerPointApp = GetObject(Class:="Powerpoint.application")
PowerPointApp.Run (PowerPointApp.ActivePresentation.Name & "!UserForm1.Show")
End Sub