Right.. you're just scaling by a factor (i.e. 5/FFFh), nothing non-linear, so this is easier.
Technically you don't even need a lookup table. But here's the concept if you used one.
Perform the calculation for values from 0 to FFF, and store them (i.e. 0.0012, 0.0024, etc)
but scaled up, e.g. 1, 2 if you want it to 3 decimal places, i.e. I've multiplied by 1000.
Make sure the table results are scaled up so that you're not dealing with decimal points.
If you want to continue doing further calculations, then you can use the scaled values.
If you want to display the results, then you know to scale back down by moving the decimal point.
The benefit of a look-up table is that it will save you compute time if you've got nonlinear
values. For the linear case, note that you could just multiply the single scaled value.
And a multiply is just 'add' instructions in a loop, if you're using an assembler.