X-Cart forums - PPC Tracking Code

I am trying to install Axandra's MArketing ROI Optimizer 2.0, here is the code that is given to me for tracking PPC conversions. Where is shows the variable a= I need to substite the 1.00 for the subtotal of the sale in the order_message.tpl. I am running 4.1.x. I was wondering if anyone new the code I could add to have this work?

Code:

<!--Start of HTML snippet-->

<img width=1 height=1 src='http://www.xxx.com/axroi/conversion.php?t=Slaes&a=1.00&w=Flooring'>

<!--End of HTML snippet-->

Thanks!

Chris Edwards