CRM 2011 Alter subgrid layout using JScript

I need to show different FetchXML queries in a subgrid dynamically, depending on certain conditions. I have succeeded to do so, using the following method:

oGrid.control.setParameter("fetchXml", [fetchXml]);

Anyway, I have to deal with one limitation: I can't get to alter the subgrid layout. The method oGrid.control.setParameter('layoutxml', [layoutXml]) does not do anything, not even produces an error.

Is there any way to modify the columns of the subgrid using JScript?

Thanks.