Updating tables from form

[MLife]

Hi,i have an order form which gets items from tblCD,on my sbform in order i select the items and type the quantity i want in the field "CD Quantity" ,in tblCD there is a field Quantity,and i want this field to decrease by whatever "Cd Quantity" increases by,any thoughts?

Thanks

 

[DES]

Personally I would never have a field in a table that is based on a calculation.

If you have a field where CD's are added to the inventory then a DSum on that field would give you the total of CD's available.

Since you have a field for CD's going out, if you DSum those and subtract that amount from the the Total CD's available you end up with what is left.