Web App DataGrid I need help pls

Hello, maybe can someone to help me.
I have a datagrid in a WebApp which contains a dropdownlist named ddlGroup, and 3  bounded columns MinAge, MaxAge and Code.  In the datagrid I can Edit, Update, Delete and Add a new row. In Edit mode, Code is generated in accordance with ddlGroup, MinAge and MaxAge. For this I need an event or I don't know what to catch the moment when text is changed in MinAge, MaxAge  textboxes or the selectedvalue from ddlGroup.



Can someone help me, pls?
Thank you!