Open a form using a vb script

Hello, Im am tryinig to open a form (wich resides in an excel file) using a vb script located in the desktop, here is the code:

Set objExcel = CreateObject("Excel.Application")
objExcel.Visible = true
Set objWorkbook = objExcel.Workbooks.Open("c:\path\name.xlsm") 

call Workbook_Open()

Public Sub Workbook_Open()


UserForm4.show()

End Sub

It can open the file, but itīs unable to open the form, displaying a message wich says that there is a missing object call UserForm4 (UserForm4 is the name of the form in excel file), the error code is 800A01A08