passing variable to dynamic text box in movie clip

I am trying to load a variable into a dynamic text box in a movie clip. I can load it just fine into a dynamic text box on the root timeline, but can't seem to get it to pick up in a dynamic text box in a movie clip. I am assuming it is a syntax issue.

Here's what I've got:

//************************************************
//load text box on root timeline
txtTrip.text = this.varTrip;

//load text box in movie clip
mcResults.txtTest.text = this.varTrip;
//********************************************************

txtTrip (on the root timeline) correctly displays the information in the variable.
txtTest (on the main timeline of the movie clip "mcResults" does not display anything.

I've also tried following with no success:

mcResults.txtTest.text = _root.varTrip;
_root.mcResults.txtTest.text = _root.varTrip;

Both the text box on the root timeline and the one in the mcResults movie clip are the same "plain vanilla" dynamic text boxes with default settings. I've checked text box names and they are spelled correctly in the code and in the instance name.

All suggestions greatly appreciated.
TIA,
Carolyn