Thanks mcbee.
That would take care of the user variables issue, but not, at least as far as I can see, the deactivation of triggers.
E.g. if I want to deactivate a trigger within my block for selection 1 but not selection 2, then I think it follows that I need separate triggers for each selection.
The best I could come up with is to clone the block of triggers once I've finished it, and apply a pre-condition perhaps using sel_index and use user variables much as you suggested.
That seemed a bit cumbersome, but it may be it's going to be the best I can do.