Extrude or Pushpull up to a point minus some distance

Hi all,

Playing around with PushPull recently. This is meant to make solid modeling intuitive and limit the need to guides/construction lines/points/whatever ?

How would you go about pushpulling this box so that the bottom lands exactly 3 units from the back face ?
Assuming you don’t want to compute the depth by math, obviously.
The SmartTrack is a bit misleading in the sense that it provides visual information of a distance from the reference point, but it’s impossible to set it precisely since the command is waiting for the overall distance.
The only way I can think of is with From and relative coordinates, which wouldn’t even work if the box had an angle.
I’ve tried with ExtrudeCrv without mych luck despite all the command options.

well… not elegant, but dropping a line 3 unit long you can snap to is an easy get.

you can also use grid snap if your object is grid aligned

or even better, measure the length of the edge and then enter that - 3 and set your direction.