Dear Mr/Ms

I am developping a tool with MSAccess as front, SQL as back-end using MASAccess ADP. I am using a report to print out a complicated query for which I use a stored procedure with a parameter. The parameter can be defined within the report properties. If however I launch the report from VBA and change the inputparameter property of the report during the "OPEN" event of the report that change is not taken into consideration in the stored procedure. How do I do this?