[smarsh]

Thanks for your response @whpalmer4 - it looks like that's as close as I can get to what I'm after.

What I mean by tolerance is the degree of autonomy by which a project is allowed to meet a milestone (e.g. + or - 2 weeks) and still be deemed to be 'in control' and thereby not need to defer to a higher authority (e.g. project board)...

In other words, the milestone is set for 1 Sept, but anything up to 10 Sept would be deemed an acceptable tolerance...