how to anounce a time changed value?

making a new global value(for the software), and then using it in (ie, amount of particles)

here is a case scenario:

making a random amount of particles existing in every frame

from a material's texture(cycles? doesn't matter), 
   i extract the value of the texture based the [texture co-ordinates]
     and then i call that (value*100000) in the particle system (amount of particles)
 
   and has to update in every frame

how should i go about it?