Hi I am struggling to find an answer to this, if it can be done?

I have a login form that contains 3 textboxes: UserID, Post code, Date of Birth

The user id is fine I can add a required attribute to validate, but I was wanting to validate that they had also entered data into 1 of the other 2 textboxes, so either post code or date of birth. I don't want to use asp.net custom validators as they are a pain, and was hoping that this could be done in html5/jQuery. These textboxes are on a .net user control, so not sure if that is an issue as I have had trouble with it finding the form if i use something like... $("#form1").validate