Is there a way to input an audio instrument into a side chain of another plugin?

OK I've been a Logic user since version 3.5 and I've recently got the most recent version (from version 5.5.1 on PC) and I was wondering why there still isn't the ability to input a signal from an audio instrument into one of the many plugins that have sidecahin capabilities? I ask this because I constantly find myself wanting to do this and end up having to bounce down the audio from the said audio instrument before being able to input it into the side chain of the plugin I'm using. I kind of accepted this long winded procedure on the very earlier version I was using but I really thought that by now on version 9.1.8 they would have implemented this feature. Now if there is a way and I'm just being a bit thick (which happens LOL) then if someone here could point me in the right direction I would be very grateful.