Calculating fields

[yanela]

I have different tables that are linked to each other (Table Relationship). It has Quantity In and Quantity Out field on a table. How can it be done so that when a value is entered to the Quantity Out, it is lessed or substracted to the Quantity In when an employee return the items done. Like for this day, I got 5 items that are to be processed and the next day or someday, I will bring back 4 that are finished product. So there would be 1 more left for me to finish. The system should also not allow enter a value in the Quantity In that is greater than Quantity Out. Please let me know if I you have questions. I'll try to make it clear as possible. Thanks much...