Report studio filter & valueprompt without selection

[mikeou]

Hi

I have optional valueprompt in my report page(not in separe prompt page). When report is opened or refreshed I need to check is there ?Param1? selected and if not use default value in filter. I'm trying to use Following code in filter but it's not working. I'm using dimensional data, please help.

if (?Param1? is null) then ([Product forecast].[Product].[Product].[Product line] = [Personal Accessories]) else ([Product forecast].[Product].[Product].[Product line] = ?Param1?)