what do you mean by multiple values?
I pass a string of values to my stored procs, but I also have a function that will split the string into a table so that I can join against it.
if the string is well formatted (ie you can get you users to enter something like:
,1,2,3,4,5,56,
you could use a simple CHARINDEX(table.field, {parameter})>0, though you might be prompted for the parameter twice, once for the report, once for the command...
command objects are a strange beast...I don't believe that they intended to be a datasource for the report, but method to populate dynamic parameter selection lists, which is why they might ask twice for the parameter.
HTH