Dave,
You should grab v4.16 as it has been cleaned up and improved very much and the best part is that it is public now. Here is one way of doing what you want (I had a quick look through my v3 manual and couldn't find it)*. In v4.xx select 'configure' (duh!), 'buttons', pick a button, then name it (probably to the directory/drive that you want, let's say DH7: for example), then for the button action choose "Command ScanDir dh7:" and you're away to the races!
* You may be able to do it with an AREXX script but I think upgrading to 4.16 would be easier.
Pete
