Query in a query

I have a query (thanks to this group) which returns the very last date in a sequence. This query works great. I now want to use it in another query where I take the last date in the sequence (the last time a child received a new karate belt) to NOW and count the number of attendances.
I have a table with attendance information:
Student Name
Month
Number of attendances for the month
and
I have the query which returns the last belt date
My question: How would I write a query which shows the attendance of the student since the last belt promotion? Would I add a colum to the original query or create a whole new query? Thank you VERY much for your help.