@AnarchoNinaWrites There are two three options.
Use one of those heroes that block movement.
Bait the AI with a worthless junk army and your real army in ambush mode next to and hope the random number generator spots in your favour.
Install a mod that lets you move at 125 percent distance by default.
That last one feels cheap but not as cheap as the AI moving one pixel precisely out of your range each time, perfectly.