Javascript for use in a PDF

We have a Pharma client who is trying to develop an interactive Acrobat PDF dose calculator for their product. I have been able to figure out some of the basic JS calculations but the full thing is beyond me.

Essentially, from the patient weight, the client would like to populate a number of other fields - the dose is a straight multiplication of the patient weight, this figure carries over into the new dose. The new dose is then rounded up to the nearest 0.25mg. Once the new dose is determined, it needs breaking down into three fields to produce the smallest number of pills to for the dose. The pills that they sell are in three weights, 0.25, 1 and 4mg and the aim is to calculate the smallest number of pills to achieve a dose recommendation. 9mg is best divided as a 2x4mg and 1x1mg. 12.75mg would equal 3x0.25mg and 1x4mg and so on.

I have produced an example PDF which I will share if you think this is something you can help with. I don't mind how the figures are populate, either by calculation or referring to a lookup table.

Do let me know if this is a project you can help with.