Can't add with a constantly changing variable

[Ffatty]

Okay, so:

I am making a game in flash, that uses several resources to build different buildings, that help you to gain resources, etc. I'm trying to make it so that the more "_global.food" you have, the faster your resources will go up. I have it so that the variable "_global.woodBoostMeter" goes up as fast as "_global.woodBoostSpeed" and when it reaches 500, it gives you 1 wood. I want it so that "_global.woodBoostSpeed" is modified by "_global.food" divided by whatever 200 is. (So that you will get resources faster for the more food you have)

Here's the code I'm using:

_global.woodBoostMeter =0
_global.woodBoostSpeed = _global.food / 200
_global.woodBoostObtainRate =1

onClipEvent(enterFrame){
_global.woodBoostMeter +=_global.woodBoostSpeed
if(_global.woodBoostMeter>=500){
_global.woodBoostMeter=0
_global.wood +=_global.woodObtainRate
}
}

I think the problem seems to be with the "_global.woodBoostSpeed = _global.food / 200". it doesnt go up slow like it should, since "_global.food" starts out at like 200.

Sorry if i wasn't very descriptive, lol.

THanks!


*** ALSO: ***
Im using actionscript 2.0