How to call a macro(check for unsaved data) before calling refresh button of EPM TAB

Hi,

I want to show a popup message for any unsaved data before USER hit the refresh button on EPM tab.

I write the macro like as below in module

Function TestForUnsavedChanges()

    If ActiveWorkbook.Saved = False Then

        If MsgBox("There is unsaved data, save the data otherwise u will loose the data. Do You Want to Save the Data ?", vbYesNo, "Warning") = vbYes Then

        bSave = True

        Else

        bSave = False

        Application.Undo

        End If

    End If

End Function

so how to execute this macro before Refresh ?

Thanking in Advance !!