input_txt var issue

I have a frame with several input text boxes w/ var id’s. Let’s say I have input_a and the var is called “ia”. Now in frame 2 I have an MC with several complex formulas and some key var. Here is the code that takes the input_a var.

//inside container_mc
var a:Number = this._parent.ia;
//this cause a plot points to go way below the allow area on the graph

That seems to cause things to go wrong, however if I hard code the same value that I would normally input, like the example below, it works just fine.

var a:Number = 10000;
//this cause the same plot points to fall within the acceptable range on the graph