How to Write business logic for the user defined fields
I have some user defined fields and i want to write business logic for these user defind fields. How can i write business logic to my user defined fields. For example there are three user defined fields 1. column1 2. column2 3. sum.
If i have entered a value 1000 in column1 and 2000 in column2, the sum of these two will populate in sum column. i.e, 3000 will populate in column Sum.
How can i achieve this..?