Refresh / reread variables within movie

I have created a little virtual shop that reads the amount of money a player has and then enables different products to be bought. Eg - if someone has 200 points they can buy a ball for 20 or a bat for 200. This all works fine for one purchase. All of the items check the score and are enabled or disabled fine. However, say I purchase the ball - the points reduces by 20 to 180 - not a problem - but the bat is still enabled even though the variable has reduced so they can’t afford it.

Is there a way of refreshing the variable so that the items are constantly monitoring the variable amounts?

Here is the code I put in an mc inside the ball mc that enables it:

onEnterFrame = function(){
if (_root.myscore >= 100) {

I put it in an mc so that if they buy the item it goes to a different frame where there is no mc to check the myscore var and therefore they’ve bought it!

I know it is the onEnterFrame that is the problem but I am not too sure what event handler would work. Any suggestions?!