Hi Steve,
I do have PCM and it can pull back trunk utilisation. However i think its a very poor piece of software. I'm using PRTG for network monitoring which I was hoping use the oid in to regularly pull back the current traffic on the trunk.
sFlow would be an option, I have written some custom tools to collect sampling data from my procurves, I havent looked too far into it but I think that using sFlow polling on the trunk ports might to the trick!
I would still like to know if there is a specific OID to measure port util tho, with this I could write a script to run on demand, and gather the current status on the trunks