Rolling up values for one last calculation

Here's the scenario---

2 tables:

table1 ( a lookup table ) 1:N

id

ingredient

gross_cost

------------------------

table2 ( one record per item )

id

rec_ingredient

rec_unit ( a number )

rec_portion ( a unit of measurement )

rec_code ( unique identifier )

Now, using various queries I can calculate values for table2 based on table1.

I need to be able to tally up all the table2 cost values which I derive from using table1 gross_cost value, then use that total as a new value for one final calculation.

I thought an join would do this but I'm thinking more and more it'll be a temp table.

Pete