Not sure exactly what your looking to do but jogging speed is only set as a percentage of max velocity. But with some math you can arrive at what percentage any speed would be.............. so you could have a DRO you enter a speed into.
You can do feed moves at any speed you want but you also have to know what position or distance.
The following example has a little of everything your looking for I think. Down script goes in a buttons down script event and the up script goes in the same buttons up script event. It will get the vale from the JogRate DRO and jog the X axis negative at 50% of that percentage and it will jog the Z axis positive at 100% of that percentage. Lets see what you can do with it........
--Down Script
local inst = mc.mcGetInstance()
local rate = scr.GetProperty("droJogRate", "Value")
rate = tonumber(rate)
mc.mcJogSetRate(inst, mc.X_AXIS, (rate/2))
mc.mcJogSetRate(inst, mc.Z_AXIS, rate)
mc.mcJogVelocityStart(inst, mc.X_AXIS, mc.MC_JOG_NEG)
mc.mcJogVelocityStart(inst, mc.Z_AXIS, mc.MC_JOG_POS)
--Up Script
local inst = mc.mcGetInstance()
mc.mcJogVelocityStop(inst, mc.X_AXIS)
mc.mcJogVelocityStop(inst, mc.Z_AXIS)