I am a novice. My apologies in advance for such a minor question

Moneris input for hosted pay looks like this:

<input type="hidden" name="ps_store_id" value = "xxxxxxxxxx">
<input type="hidden" name="hpp_key" value = "xxxxxxxxxxxx">
<input type="hidden" name="cust_id" value = "Member: 1234">
<input type="hidden" name="email" value = "someone@someplace.com>

My simple question:  How do I get a variable into the cust_id and email input fields.

Environment is aspx, html, and vb code behind.

Would be appreciative if someone could show a sample code or point me somewhere.

thank you