I think I'm missing something too...

The purpose of the newsequentialid() is to be sequential in the context of a given table, yes? Therefore the SP would need to know the last uniqueidentifier used in a particular table in order to generate the next sequential uniqueidentifier, yes?

Perhaps the SP would need to accept a table name as a parameter, which it would query to find the last uniqueidentifier that would then use as the 'seed' value in the temp table, then inserting a new row to get the newsequentialid.

No?

Sorry if I'm missing something