Yes, this is possible, but it's not quite that simple. The current version provides a fixed set of four parameters: @PortalID, @TabID, @ModuleID, @UserID. This basically gives you access to everything you need though. First, you need to get the user name using the UserID, then you can call the stored procedure. So here's the T-SQL to do exactly what you want:
DECLARE @uname nvarchar(256)
SELECT @uname = UserName FROM dnn_Users WHERE UserId = @UserId
EXEC storedprocedure @uname
You can use similar techniques to get data relating to the current Portal, Tab, and Module as you need.
A future version will have a more robust parameter system that will allow you to get a parameter containing the username (and many other fields) directly, but until then this should work (sorry, that feature isn't going to make version 5.0, but hopefully it will be soon after that).