No need. Solasta does it; the controls are just a little bit awkward, but once you got used to them, there is no problem.
The first sets your x and y position, as it does now.
I'd rather prefer the other way around; first you select the altitude (Alt+Mouse Wheel, or PgUp / PgDn, whatever) and then you just move the mouse. Actually, it could be done in any order; cursor locking is unnecessary.
