Modify style of a component?

ok, i have a comboBox with the instance name “testBox”, and when I do the following:

testBox.setStyle(“themeColor”,“haloOrange”);

I get the following errors when I try to view the movie (control->Test Movie).

Error Scene=Scene 1, layer=Layer 1, frame=1:Line 20: Statement must appear within on/onClipEvent handler
testBox.setStyle(“themeColor”,“haloOrange”);
Total ActionScript Errors: 1 Reported Errors: 1

I don’t understand what this means.

If I could get some help, it would be much appreciated.

Thanks,

Justin Fox