SSRS can pass a multi-select string parameter selection to a stored procedure as a comma delimited list of string values that can simply be used in an IN clause in a stored procedure. It doesn't seem to be so simple or numeric values though because the list has to be passed as a string parameter. One method that should to the stored procedure as string.
One method that I can think of is to construct a "dynamic SQL" command in the stored procedure so that the list numeric values can be embedded in an IN clause but I would prefer to avoid that. Another method seems to be to develop a table valued function that converts the comma delimited list into single column table that can be used as a sub-query in an IN clause.
If anyone has other suggestions I would like hear of them.
R Campbell