Calculate to database

i want to calculate fields and save to database.
{total_net} = {each_net} * {qty};

i did use this and calculated but not saving to database.

how can i save total_net to database. Thanks

Hi, if your field is created from a table (Not external field ) total_net should save.
Maybe you have some attributes for that field like read only.

What event do you have this code on?

i did in onload event