How to Validate Multiple Forms without submitting

How to Validate Multiple Forms without submitting

I've a page that has 2 forms.  If the user clicks the bottom form the validations appear and everything goes red but the Top form is a required field but it doesn't as it's a separate form.
 
How can I validation form0 and form1 together to show to the user the required fields.
 
When the user clicks form0 it goes over to a pagedLIst, the user returns and textfield gets populated with the product that as selected.
 
So when they hit form1, that value gets passed through as a hiddenfield..
 
<form id="form0">
            ...text box input to search for your product, returns to this page populated the found product
        <input class="button" id="FindProduct" type="submit" value="Find Product" name="action"/>
</form>
 
<form id="form1">
......text boxes etc
        <input class="button" id="Record" type="submit" value="RECORD" name="action"/>
</form>
 
Help!