Row change event in WDP ALV

Dear Experts,

Can anyone help me how to raise event on row change event in WDP ALV.

I have two columns namely ' From date and two date' in my ALV table.

I have defaulted the "from date" to 6 months from current date.So when i change the "From date", the "to date" should be automatically get changed to 6 months from "From date" field.

Thanks

Katrice