Hi Pilou, not sure if you are talking about a cube here.

Cant you draw some lines (with "fat lines" script?) or use rectangles as lines
combined with ARRAY / join to get a fast grid object to then be used "groove" lines. Copy 4 times. Weld/join that to other surfaces then Extrude groves up/down to suit? Maybe use some control points to make things interesting. Likely I can create your grid really fast in 2d. If I knew what dimensions you want happy to experiment on automating that 1st part...

Kindest regards

Stefano