You can remove it from the container and put it into a really clean glass bowl, heat around 1/2 an inch of water in a pan - make sure no water contaminates what you are heating and gently warm the bowl/tub with the balm, it should melt really easily and become a liquid/much softer at which point you remove it and dose it with your perfume, ensuring you thoroughly mix the perfume into the melted balm prior to it setting - it will bind with the fats/oils uniformly.
.7 of a fluid ounce = 20.7015g
The safe range in Australia here is .200 mg (perfume) for a skin product (at 20.00g) but as we don't know any of the variables exactly, its going to be all approximation and guess work on your part.
I would go with 10 sprays of an EDT to begin with or play it by smell, there really is no accurate way of doing it without knowing the exact perfume concentration and being able to account for the alcohol evaporation.
At the end of the day it will work, it will just be down to how many 'sprays' you do.