Requiring Terms are read before proceeding

I have a web page where the visitor pays a fee before proceeding. I'd like to add a requirement that the visitor "check" that he has Read The Terms, before he can proceed to pay. I have this html code of the pay page here:
(There is also a php page that works with this html page).

<!--Begin Wide Column-->
<div id="column-wide">
  <div id="generic-container" style="height:500px;">

  <div style="margin-left:12px; float:left;">
    <img src="themes/[var.user_theme]/images/icons/members_32.png" alt="members" width="32" height="32" align="absmiddle" />&nbsp;&nbsp;<strong>Pay Fee:
    &nbsp;<!--[var.members_total;comm]--></strong>
  </div>
  <div style="margin-right:12px; float:right;">
  </div>
  <br />
  <br />

  <div id="members-search">
<br>
	<table style="margin: 10px auto;border:1px solid lightgrey; background:lightyellow">
	     <tr>

		  <td width="150px"><br><u>Details</u></td>
		  <td width="150px"><br><br><u>Pay Fee</u><br><br></td>
		  <br>
	     </tr>
	     <tr>
		  <td><br>Pay Fee<br><br></td>
   		  <td>
               <form action="payment/paypal_start.php" method="post">
                 <input type="hidden" value="[var.user_id]" name="uid">
                 <input type="hidden" value="1" name="cre">
                 <input type="hidden" value="Pay Fee" name="itnm"><!-- Must match paypal_ipn.php name  -->
                 <input type="submit" value="0.01" name="valu">              <!-- Set dollar amount of fee here.  -->
               </form>
            </td>
	     </tr>
          <!-- ================================================================= -->
	</table>
<br><br>
</div>
</div>

<!--End Wide Column-->

Code (markup):

And I grabbed this line of code from the Registration Page and added into the pay page, but of course it didn't work, by me just adding it:

     <div style="margin-left:30px; float:left;"><a href="page.php?page=3" target="_blank"><span style="color: #800000;"><u>Read These Terms</u>&nbsp;</span></a>
	          &nbsp;&nbsp;<b><span style="color: #000000;">Click Here</span><input type="radio" value="yes" name="terms" [var.checked] /><span style="color: #000000;">To Agree To The Terms</span>
        </div>

Code (markup):

Can you help me integrate a "required to read" instruction before proceeding, into the pay page?

Thanks

 

Could you post your whole registration page code? Or PM it to me if you wish to keep it private. I can try to help you out.

 

When you create the form, add disabled="disabled" to the submit button.

Then when the user clicks the checkbox you can use the onclick property of the checkbox to set the disabled property of the submit button to "".