Dynamic text changes back to initial text on keyframes

Hi,

I’ve created a dynamic text field (named text_txt) on stage - gave it a value of “123”;
There is 1 keyframe (frame 1) followed by 9 frames.

I’ve added a tiny piece of actionScript:
text_txt.text = "99";

Running it - all works great - I see 99 in that text field.

If I add another keyframe (lets say on frame 5) - the text inside text_txt changes back to 123
Instance name there is still text_txt…

Please see attached file,
Any ideas?

Thnx,
EZ