Executing a stored function from a query

Anyone know if you can execute a stored procedure within another stored procedure / query??

Trying to do this

SELECT .........

WHERE (COMPANY_ID NOT IN (SELECT..........)

I want the NOT IN Query to be stored as a seperate procedure/query

I can do it in access I know but I need to do it in Transact-SQL

I think it would be like this:

SELECT .........

WHERE (COMPANY_ID NOT IN (execute sp_whatever))


don't have my SQL Server up right now or I'd double check it....