Can I trigger a VBA script without pausing Outlook for the duration?

This might seem a little backwards, but I've spent the last 9 months developing a complicated system of very effective VBA scripts for Outlook automation, but now I'm asking a fairly simple n00b question.

Can I have Outlook run a script, but leave Outlook usable whilst running it?

Background: despite having the VBA code for Event triggers to launch scripts when an email arrives, I've not found it to be reliable enough (admittedly I've not tried it again since I upgraded from 2003 to 2010 - so I might try it again). So instead, I use an Outlook Rule to trigger the script when an email arrives with certain keywords (e.g. when an attached report arrives with AUTORUN in the mail subject). But this approach hangs Outlook throughout the script, and if something is taking longer than expected to run, e.g. if a shared drive is particularly slow (or as happened last week, if I've made a mistake in the setup and I'm running an Update query that takes 6 hours to run!!), I've rendered Outlook unusable for a whole day. I don't know if switching to Event triggers would even change that.

I've thought about creating a new Outlook.Application instead of using the intrinsic Application object but my experience with Excel VBA tells me that that wouldn't make any difference. However, with no formal training in VBA maybe I've missed a trick there too...!!

I've also thought about manually starting a new session of Outlook but I'm worried that'll just start running the same scripts twice......

I've also just thought that maybe using Shell is the answer...?

Help appreciated, and sorry if I've posted this in the wrong support forum