Required field Validation implementation Client Callback asp.net

Question

I have a grid which have required field validation. This grid is repopulated when user clicks on Add in pop up and saves, it repoulates the grid of the parent page using Client Callback mechanism. At this point it does bind required field validation at all. There is post which discuss about the behaviour but it does not specify about Required field thing. http://msdn.microsoft.com/en-us/library/ms366515.aspx Can any one suggest how to go about this Thanks in advance