Mark as processed

Good day,

I have a tblDeductions, where I would like to record some deductions made to staff hours. We have a time sheet number (not relevant in Access) from which we deduct a certain amount of hours for a particular course as set in the tblCourse.
So far, I have it all working, however I'm struggling to figure out how I mark a deduction done tick box if that staff member (StaffID) has been deducted the full amount of hours. I have a Update query that totals up all the deductions made for a particular staff member, and the idea is that the update query ticks all the boxes to mark Deduction done. This part is not working and I'm struggling to figure out the best way to do this.
On the form where deductions are recorded, the cbo box to select a staff member should only show the staff members who have not yet fully deducted the course. Once selected, a different txt box should shor the remaining hours to be deducted.
This is the first time I'm using this forum, How would I go about uploading what I have so far?

I look forward to some much needed help.
Thank you in advance.

Marco