Stretching a texture map in one direction only

[MGuilfoile]

In VW 2023, I want to mask and paint several walls with a three-color band. I have created a map (see attached) that is for one of the walls, but I figure I can just stretch the map horizontally to fit all the other walls. I'm not concerned about the "waviness" of the two curves that divide the colors. I'm fine with the curves getting shallower on long walls and taller on short walls. Working with texture maps on walls is already very clumsy to me, but I am really thrown that I can't find a way to simply stretch the map in just the horizontal direction. I can tile it, but I don't want to tile it. I'm sure I must be doing something wrong (I mean, you'd never be able to make a woodgrain board look like woodgrain if you could not stretch the map in one direction.) Am I missing something simple that is not possible on walls? I'm certainly missing something simple, for sure, but could someone help me out?

Thanks!

MHBrown