Does my MACRO syntax have problem?

I write my first SWP macro. It is just a button to set the properties.  The problems are

1. the user form does not show every time

2. There should have some problems in the syntax

The swp file is attached

If you don't want to download the file , here is the code. Please help

================================================

Option Explicit

Sub main()

Dim swApp As SldWorks.SldWorks

Dim swModel As SldWorks.ModelDoc2

Dim swCustPropMgr As SldWorks.CustomPropertyManager

End Sub

Public Sub ALUM(promgr As CustomPropertyManager)

promgr.Add3 "MYMATERIAL", swCustomInfoText, "AAAA", swCustomPropertyReplaceValue

promgr.Add3 "MYDATE", swCustomInfoDate, "07/02/2015", swCustomPropertyReplaceValue

End

End Sub

============================================

Private Sub ALUM_BUTTON_Click()

Call ALUM(swCustPropMgr)

End

End Sub

========================================

SolidworksApi macros