Nested tuplets

[Vaylor Trucks]

suppose I want something like this:

\key a \minor
\time 4/4

% turn beats 1 and 2 into a quarter note triplet
\times 2/3 {
a16[ b c d]
a[ b c d]

% turn the third note of the quarter note triplet into an 8th note triplet
% (three 8ths in the space of 1 qtr)
\times 2/3 {
a8[ b c]
}
}

when the music is printed - the 3 from the quarter note triplet and the 3 
from the 8th note triplet are mased on top of each other.  Can I space them 
out so that doesn't happen?

Vaylor