Variants available in BEX execution but not in Web execution

Dear Colleagues!

I have experiences something strange. When I execute my query in Excel I am able to save a variant in the variable screen (I want to hide a field). But when I execute my query on the web I am NOT able to save (or choose) variants! What can cause this? Versions?

What I want is for the infoobject customer to not be changeable for the person executing the report. It should only be filled out by the portal (logon name pushed into the variable).

Regards Silje