Having some problems with envelopes

I'm currently having some issues regarding envelopes, which seems to be
exacty what is described here:

http://lists.w3.org/Archives/Public/public-audio/2013JanMar/0053.html

I'm playing sequences that i schedule ahead in time, but i don't see any
way to get the envelopes right. Some questions:

- what happens exactly when i cancel scheduled param-changes? it's totally
unclear for me from the specs what happens to the value when i schedule a
cancel on a moment when it will be in the middle of a change (a linear ramp
for example)
- is it currently impossible to implement a correctly working envelope when
scheduling ahead in time?
- is there any way to access the queued/scheduled param-changes on an
audioparam?


regards,
Peter