math calculations between successive siblings

I have XML like the following:

<event>
    <starttime>9</starttime>
    <duration>3</duration>
</event>
<event>
    <starttime>13</starttime>
    <duration>1</duration>
</event>

In converting 'event' nodes to HTML table rows, I would like to insert
filler rows of the appropriate height between the 'event' rows so that
the resulting table scales appropriately. The height of these filler
rows is proportional to the difference between the starttime of an event
node and the sum of the starttime and duration of the previous event
node, e.g.

fillheight = propconstant*(node[i].starttime - (node[i-1].starttime +
node[i-1].duration))

How do I get a template to communicate with future instantiations of
itself, I haven't been able to get variables to work and I'm not sure if
params will do the trick.

Thanks


--
Paul Madsen

Coventus Intuitive Networks
340 Terry Fox Drive, Kanata, On, Ca
K2K 3A2
e) paul.madsen@xxxxxxxxxxxx
p) (613) 271-0180 x296



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