Math Mask that can be nudged

is there is a way to mask off the lower (say) horizontal fifth of a texture - without using another bitmap?
Ideally I’d be able to nudge this up or down like I can with a bitmap.

Thanks

Here’s one way of doing it. You can “nudge” it by making the node that goes into B a parameter which you can change from code or BP.

Yes, yes, yes!
Thanks diesel head.

Epicureans - please log a bug that if you use a mask B in the above example, the if node will throw an error

Epicureans - please log a bug that if you use a mask B in the above example, the if node will throw an error

I believe the reason is Texture Coordinate has only red and green channels?

10 - 4! Jacky