How to know the Reporting services version at runtime

HI, can anybody help me?
I have a problem. With the sqlserver 2005 sp2 some behavieur are differt from previous versions.
For example with service pack 1 there isn't the "select all" option for multi value parameters, so i add MY select all, but with service pack 2 there is the "select all" option for multivalue paramteres, so when my reports are running under a server with service pack 2 in the list of multivalue parameter I'm going to find "Select all" and "MY select all"
It is possible to know at runtime under which version my repors will be running? so I can use or not MY select all. (i cannot force client with a particular version)

Thank in advance

If you can call any webservice method (e.g. ListSecureMethods), you will get back a serverinfoheader, where you can look into reportserverversion property to determine the server version.