Custom Validator as requiredfield validator problem

I want that my custom validator control sets up Page_isValid variable accordingly.
On server side custom validation is ok with my custom validator control ,Page.isValid property is set accordingly

problem is that Page_isValid variable (client side) isn't set, to reflect validation status

When I use requiredField Validator control , my Page_isValid variable is set accordingly.

What do i need to do with custom validator control (event) so i get this same feature as requiredfield Validator control