omit fingering

[Gianmaria Lari]

On the accordion scores to indicate that the button to press is on the counter bass we put a small dash under the finger number. This is how David Kastrup suggest me to do it:

\version "2.19.81"

{a_\markup \underline \finger 3}

This is perfect.

But, is there any way to make it removed when I specify  "\omit Fingering" like in the following example:

\version "2.19.81"

{\omit Fingering a_\markup \underline \finger 3}

?

Thank you, Gianmaria