Access Calculation and insertion

I have 2 tables Accruals and Usage
Accrual table(Emp_no,Beg_bal,Cur_bal)
Usage table(emp_no,date,type,hours_used)

I would like to sum hours_used for specific emp_no and type from usage tabel then subtract that sum from from the beg_bal and insert that into cur_bal of the accrual table

Any sugestions thank you