Software sampler, hardware sequencer - sequencer recording its own playback

So, I picked up a fully functional Roland MC-50 sequencer off the side of the road. Up 'til now my total lack of scrilla means i've been totally software based, but in playing with the sequencer, it feels like it might be heaps faster to use as a 'scratchpad' to throw together ideas than straight software. Buuut, i'm a a total midi nubcake. I've got a soundcard with midi i/o, and have the basic handshake set up, and I'm triggering samples from a cheap pad midi controller and a sampler vst. By routing the sampler track's Midi Hardware Output send to my soundcard's midi-out I can hit pads and it triggers the sampler AND sends to the sequencer, which is good. Using the sequencer's play button also triggers the sampler so I can play back from the sequencer too, also good. The problem is that when I try to multitrack with the sequencer itself rather than Reaper, the sequencer's midi playing the first track triggers the sampler (so far so good, so I can hear the track I just laid down and play along to it) and ALSO records it (not so good). So every new track has every track before it on it, and each new iteration lags slightly behind the last. I admit it DOES soundkind of cool three or four tracks in, but I'd like to have the option of NOT doing that. Basically, my question is - how can I get it so that my little pads send to the VST plugin and either the plugin or the pads send to the sampler, but the sampler sends back to reaper so I can dump the sequences to midi in reaper once I'm happy with them, as a backup for the floppy disk in the sequencer WITHOUT sending to itself? Something to do with midi channels? If any clarification is required, let me know.

impending cross-post? 

Should I have posted this in the MIDI/OSC forum? It feels more like a newbie question than a midi/osc question.