Unescaped expression problem

Unescaped expression problem

  
Hi! I'm using the pivot table example that i've found in this forum to create a table with a variable number of columns. It worked fine but now i have another problem. Imagine that i need to put a checkbox on each cell i've created... How can i know if a checkbox has been checked or unchecked?

The pivot table example can be found here:
http://www.outsystems.com/NetworkForums/viewtopic.aspx?TopicId=3104

I'll apreciate any kind of help. Thanks in advance!