I have a large assembly (over 1000 parts) and I needed to change the hole size on all the parts - and there's tens of thousands of instances of it!
I obviously considered going through, editing every part - and then thought I'd spend the time writing a macro instead!

This traverses an assembly or part, finding all the dimensions that match the criteria you enter on the form and replaces them with a new value.  Seems to work pretty well.

It will work in whatever dimensions the document uses - mm or Inches at least.  Doesn't work with Chains, Furlongs etc!