How can I access the parameter/s I have created for a custom WebADI?

I have created a custom WebADI that calls a custom stored procedure to process the rows of the spreadsheet.   That part seems to work fine.  The part with which I am having a problem is the "Parameter" field.  I am actually borrowing the seeded parameter "MA_PARAM_WNDW" aka "Web ADI: Mass Addition Parameter Window" to allow the user to enter the "Corporate Asset Book" which the spreadsheet will be updating.  So far, I can't figure out how my stored procedure can see what the users enters for this parameter.  Right now, we only have one Corporate Asset Book, so it's not a show-stopper.  But I'd really like to know how I go about allowing my program to see the data the user enters in that parameter.