Please help in a databound form

Hello.

i am new to asp.net and i am developing an inventory system.

i have used a databinding feature of .net , and i am inserting ,editing and deleting via built-in links of

databound controls.

question is, i want to check before e.g insertion some critaria first in my database and than wana decide whether to

save the new data in database or not, now i dont know how to call my custome method for checking some critaria ,before the insertion (e.g) of the new data.

hope u will understand.

mansoor