cancel workflow when quantity payment block is cleared outside the workflow

[Torsten Schnorpfeil]

Hi folks,
 
here's the thing: Does anybody ever developed a workflow scenario where =
you raise workflows due to quantity variances (blocked due to quantity)?
 
How do you solve it, if the workflow instance is still running and the =
payment block is cleared/released outside the workflow.
 
I was thinking about using change documents, but then how can you =
differentiate between the clearance inside and outside the workflow?
 
Any hints highly appreciated!
 
Cheers,
Torsten