You can get the model type from the view and then use the IF condition.

Option Explicit
Sub main()
    Dim swApp                       As SldWorks.SldWorks
    Dim swModel                     As SldWorks.ModelDoc2
    Dim swView                      As SldWorks.View
    
    Set swApp = Application.SldWorks
    Set swModel = swApp.ActiveDoc
    Set swView = swModel.SelectionManager.GetSelectedObject5(1) ' Make sure a view is selected
    Debug.Print swView.ReferencedDocument.GetType ' 1 for part and 2 for assembly.
    
End Sub

Also please move this thread to API section (use move discussion on right side)