changing file name of midi output

[Gianmaria Lari]

If I compile the following code in Frescobaldi....

\version "2.19.81"

\score { {a b } \midi{}}

\score { {a b } \midi{}}

\score { {a b } \midi{}}

lilypond generates the following midi files:

document.mid
document-1.mid
document-2.mid

Is there any way to change the numeration like this:

document-01.mid
document-02.mid
document-03.mid

?

Thank you!