Anyone used Realex with Ecart?

hi,

My client has just changed payment providers to a system called Realex. The site I've built currently uses WorldPay which being supported by WebAssist is obviously great but now I need to update it for this new system which isn't supported.

I only need to pass a certain few values via hidden fields as follows:

<input type=hidden name="MERCHANT_ID" value="<?=$merchantid?>">
<input type=hidden name="ORDER_ID" value="<?=$orderid?>">
<input type=hidden name="CURRENCY" value="<?=$curr?>">
<input type=hidden name="AMOUNT" value="<?=$amount?>">
<input type=hidden name="TIMESTAMP" value="<?=$timestamp?>">
<input type=hidden name="MD5HASH" value="<?=$md5hash?>">
<input type=hidden name="AUTO_SETTLE_FLAG" value="1">

For instance I've tried to add the following to send the 'amount' but it isn't working:

<input type=hidden name="AMOUNT" value="<?php echo $oj_uk_08->GrandTotal() ?>">

Has anyone else worked with the Realex system that could advise?

thanks.
Greg