Hi,

It is possible. You will need to handle the validation at OnEditingFormShow client side event. Please see the snippet code below.

function WebScheduler1_OnEditingFormShow(controlId, action, eventView, eventType, newType)
{
        var WebScheduler1 = ISGetObject(controlId);
	if (action == "New") 
        {
	    window.setTimeout(function() {
		            ISGetObject("dlgEditing").Window.SetCaption("New X");
		        }, 10);
	} else 
        {
	    window.setTimeout(function() {
		            ISGetObject("dlgEditing").Window.SetCaption("Edit X");
		        }, 10);
	}
        return true;
}

Hope this helps.

Regards,
Handy