Kaamos, please run through tutorials. This is a most basic question.
There should be two states for the power button: active and inactive. The power button sprite should have a boolean variable.
In the event sheet, create a variable (or make a sprite variable) called something like "power" and every time you get a white blood cell, add 1 to power. After it reaches 10, allow it to be activated, similar to this:
If power < 10, spritePowerOn is inactive
If power >= 10, spritePowerOn is active
I'm not going to explain further, you should know what to do with this information. Again this is a very simple to accomplish task. Little hint: you probably have less sprites/variables than you need, so write the ONE process down on paper and organize it from "do this first, then this, then this" etc. If you ever say "randomly put here" or "slow down to whatever" that should be a HUGE sign you need a variable somewhere to handle those randoms, or those speed references, etc.