[ic] What's wrong with this syntax ?

[Michel COMBE]

I would like to do a computation based on the contents of the tag [subtotal]
in the cart template.

The code in the cart template, which displays the subtotal,  looks like this
:

<td class="contentbar2" align=right><b>[subtotal]</b></td>

Immediately after this code, I want to display the subtotal multiplied by a
constant (say 1.10), so I wrote :
<td class="contentbar2" align=right><b>[calc] [subtotal] * 1.10 [/calc]
</b></td>

Well, it doesn't work...
 It looks as though as soon as I use the [calc] tag, the [subtotal] tag
become unreferenced and nothing is displayed.

How should I do this simple computation ?

Thanks for your help
Michel Combe