How to calculate remaining items in stock from issue form shows in remaining stock

[master_2013]

I want to calculate remaining stocks in stocks form which issued from issue form and shows in remaining stock field which deduct from total stocks when a stock is issued to someone. I am using data bindings with access here is the screenshot for this forms

 

[jmcilhinney]

Um, you use subtraction. If you have 10 items in stock and 1 is sold then you now have (10 - 1) = 9 items in stock.

 

[master_2013]

But how can you explain with an example please

 

[jmcilhinney]

Are you really saying that you don't know how to subtract one number from another?

 

[master_2013]

Are you really saying that you don't know how to subtract one number from another?

i know how to subtract one number from another but how to subtract one number from another in two other form like as i mentioned on the screen shot.that's the big problem im facing.