I think I understand what you mean but I am confused why you need to control the hole dimension based on G. It seems extra work to get X then multiply by G. But in your equation editor you could have a value for the Hole say "H" then have an equation with H/G to get the X value then multiply G*X. But as I said this seems a lot more work than using the value for the Hole directly as a global variable. Does the value of the hole change based on G? You could control this by some logic I.e. IF statements.
Just for for example your equation editor could read to get what you want above. But in the end the value = "H" anyway so I am confused as to why you would want this.
"H" = 37
"G" = 1135
"Hole Size" = "G" * ("H"/"G") - but this is the same as G*H/G = H (so the same as just writing H)