If I might suggest, it is possible to have dimensions for a part be calculated upon a single base dimension all within Inventor. The spreadsheet idea is an excellent way and of which I was not aware. If you take notice in the nice screen capture in the previous post the dimension can be a numerical value or an equation. Substitute a formula using dimension variables and you achieve your stated purpose. Change the value of the base dimension and the entire set updates...
for example
d1 = d0/5
