Mask - dynamic text

Hi all,
Is there a way to have a movieclip containing dynamic text as a mask?

I’ve tried using AS as well as setting the mask in my timeline, but it wont work.

e.g., this is basically what I have.

this.textLinkMask.maskText.text = navigationList*

I want my slider (for a button) to be masked by dynamic text - but it doesnt work.

Is there a way I can do this?