Accessing innHTML or innerText in Java script. This is not working for me?

I am retrieving two values from two columns of my GridView. I then want to send these values to another page using response.redirect. If I trace into my Java Script code, and do a quick watch on the inner html for my grid column values, I can see that the innerhtml is correctly retreiving the values for cells 2 and 3.. So for example in the first row of my GridView, their is a persons name in column2, and their age in column 3
However if I try to retrieve the [3] column value into a variable, I get an error message that the value is undefined?? Yet using my quickwatch window i can clearly see that the numeric value for the inner html is the number "35"?
So why am I getting the undefined message when I try to access the inner html value? I have also tried "innerText" and that also comes back as undefined.
 
function Decision(selectedRow) {    debugger;
   var theGrid = document.getElementById('<%= GridForStu ...