Changing Dynamic Text not working

This is a problem I often come across but have never found an answer through extensive searching of the net.

I have a simple line

_root.txt_progressbar.text = “Parsing CSV file to grid.”;

Yet this sometimes works and sometimes doesn’t work. Seems to have issues if I put it in a function. It is like it doesn’t have enough time to action this line. Is there some kind of delay I can use to wait for it to be done?