Hi Charan,
I think you trying to validate data at the user dialog step stage. Appropriately , by this time all data validation should be completed. My doubt is let us say if the has pressed Approve button, now you want again validate some data and come out with a result whether validation is success or not. Which means you are contradicting dialog user decision. Can you please explain , what is your exact business requirement. So that we help you better.
Thanking you
Vengaiah