Masking on i-phone, i-Pad

Is not yet possible masking a texfield in i-phone,i-pad...right?

I want to to create a small section when i can see the text and with buttons made the text scrollable.
I have do that but in i-phone the mask of the section don't work..

The only solution is to put a background,the textfield, and an image with 100%'s height and width whit the right hole,where it must be the text?

Or there is a better way?

thank's to all as always!

Thanks a lot Klaus!You're the best.