>Thanks! that works fine.

You're welcome.

>What is the funcion of those curly brackets?

The curly brackets indicate ODBC Escape Sequence, in this case Procedure Call Escape Sequence.

> When do they need to be used?

That's only way to get return value from stored procedure or UDF. For other uses see http://msdn.microsoft.com/library/default.asp?url=/library/en-us/odbc/htm/odbcodbc_escape_sequences.asp