Could you add a block that says how far a sprite is from another sprite?

(x position from <touching [sprite] ?>)

This already exists, it's called “distance to sprite/mouse-pointer” and is in sensing.

If you mean a block like this:

(distance from [Sprite2 v] to [Sprite3 v] ::sensing)

Just save it in a variable like this:

Since this is resolved, I'll close it to help highlight the answer and prevent future responses. If you need it re-opened, though, you can report this and ask.