Getting data from two table fields with calculation

[dallo]

hi, can someone pls help me out.

i am trying to display the result of the subtraction of two tables, then update a field .

What i expect it to do is this MY_WALLET = MY_WALLET_COST - TREATMENT_COST, then it should further update MY_WALLET_COST


Thanks,
Dallo

[a.gneady]

Please see the example for the before_insert hook: http://bigprof.com/appgini/help/advance ... ore_insert