How to insert \ell in text box on figure in matlab?

Hi, I have a plot in matlab and want to insert a text box write inside \ell symbol. Till now i couldn't do it. I wrote '$\ell$','interpreter','latex' but it doesn't accept. I appreciate if anyone can help. Thanks.

[Jan]

Where did you write '$\ell$','interpreter','latex' and what does "doesn't accept" mean? Please post the code and the error message. Do not let us guess the details.