Cannot set .text property of txt field on button

Hi,

having problems setting the .text property on a textfield that is on a button symbol…

btn_top.txt_1a.text = "hi";

I copied the textfield on put it straight on the stage and doing this I was able to set the .text property, so I know that the other properties of it are correct - dynamic etc.

btn_top is the instance name of the button.

thanks