Development is looking into this. If we can make it work, you would need to add a &custom= parameter to all of your E-junkie Add to Cart button URLs on the relevant site, like so:
Note that all Cart buttons on a given site must use the same &custom= value, but if you use E-junkie to sell on multiple different sites, you could use a different &custom= value for each site. If we can make it work for PayFlow Pro, we would then pass that value to PayFlow, possibly in the Comment1 field if possible, or possibly in another field if necessary. We'll post a followup with details here when Development has this sorted out.