Using FB 2.0.3 on Gentoo, Qt 4.3.2

I have a stored procedure that takes a number of input parameters and a single
return value (which happens to be the Id of the record affected).

I am calling this procedure using Qt QSqlQuery with the following SQL:

execute procedure "AddFixtures" param1, param2, paramm3 etc

The SP executes OK but I can't figure out how to get the return value - I've
tried every combination I can think of based on the Qt help information.

Can someone please point me in the right direction?

Regards
Tom Munro Glass