I need a little help.

I've been looking for the variable for the order total, but I can't figure it out.

I need to use the Moneris Hosted Paypage and I've been able to put the button on the checkout_confirmation page, but I need to add the order total to the variable that passes to the Moneris Gateway.

This is the the code needed to initiate the process to go to their secure site for payament.

Can somebody help me get the order total value in the "charge_total" field?

<FORM METHOD="POST" ACTION=https://esqa.moneris.com/HPPDP/index.php>
<INPUT TYPE="HIDDEN" NAME="ps_store_id" VALUE="my_id">
<INPUT TYPE="HIDDEN" NAME="hpp_key" VALUE="my_hpp_key">
<INPUT TYPE="HIDDEN" NAME="charge_total" VALUE="1.00">
<!--MORE OPTIONAL VARIABLES CAN BE DEFINED HERE -->
<INPUT TYPE="SUBMIT" NAME="SUBMIT" VALUE="Click to proceed to Secure Payment">
</FORM>