Textbox Format Property "Underline"

hello folks,

when right clicking on a textbox one can chose on the fonts tab a text effect called "underline". I'd like to access and control this via a program. However, this method is not listed in the developers reference the Textbox Format Properties. Does anybody know whether this can be accessed by some other property or method?

Thanks in advance

Raiko

P.S.

It goes without saying that I'm using MC15