Extract the first notes from a musical expression

[Gianmaria Lari]

Consider a simple code similar to the following one: 

\version "2.19.82"

myVar = \fixed c' { a4 b c' a | a4 4 b c | b4 a b c' | ........ 

{\myVar}

This will generate a score containing *all* the notes specified in myVar.

Now, suppose that I don't want to generate all the notes in myVar but only the first 8 quarter notes (the first 2 bars) . Is there any function that can do it? something like "\extractMusic \myVar 4*4".

Thank you, g.