Accumulator field in BAQ?

I have a query that has Month to Date earning summarized by month.  I used the FiscalPer as the parent table, then joined for this piece the InvcHead table as a sumarized table  I am struggling with two pieces.

1 - an accumulator column that would show the year to date earnings
I tried various joins on the tables (thought I had something with joining on year, then using a formula to cutoff at the month), but no joy.
2 - Listing a column with prior year information.
this would be a simple function in SQL, but I don't have access to the SQL DB, so I'm stuck with a BAQ...

Any ideas you can offer would be appreciated.
Andrew Fagan