How to create a double glissando?

[Arjan Bos]

Dear list,

I would feel priviliged if I can tap into your wealth of knowledge on  
all things lilypond. The thing that's bugging me at the moment is that  
I cannot figure out how to create a double glissando where the first  
glissando goes from note 2 to note 4 and the second glissando goes  
from note 3 to note 5, all within the same voice. This is a silent  
glissando that's meant to indicate that the guitar player's fingers  
slide up or down a fret.

Please see attached picture for an example.

Kind Regards,

Arjan Bos