[mtasc] Dynamic variables?

[stuff at trackingsolutions.ca]

I need to create thumbnails for a gallery and when you click the thumbnails 
they load the main content according to the thumbnail clicked. I am loading 
the content for the gallery from an XML file. The file is now loaded into an 
array. I am now trying to assign variables to each movie clip to reference 
the thumbnail pressed. I have not been successfull in creating these 
variables from examles of actionscript from the web. Can someone help me to 
assign these variables so that I can populate my gallery?

Example code:

var tester = _root.createEmptyMovieClip("tester",2000);
_root.tester.textvar = 12;
_root.tfCaption.text = _root.tester.testvar;

This outputs undefined as the value of the variable. How would I define this 
in MTASC?

Thanks