dimension entry order for rectangles, boxes, etc.

Any way to enter y before x when defining? For example: if I'm drawing a partition between two walls that are running in the Y direction (vertical in top view)... the walls are randomly spaced, and I want to make a box between them. I know I want my partition 25 mm thick, but I have no idea the distance between them.

Any way to specify the 25 mm and let me pick the length (x dimension) with an osnap off the drawing?

Right now I either have to dim the gap, then key it in (error prone, plus sometimes impossible if the walls don't fall on the grid) or I have to make it close, then scale1d the partition to touch with osnaps. Not really ideal either.

I guess a script could make a box/rectangle with y dimension entry first... Maybe this already exists.