maximal beam length

[HEINECKE Johannes FTRD/DMI/LAN]

Hello again,

I havw got another pmx/m-tx related question.
Is there a possibility to determine generally how many
8th (16th etc) are under one beam? I think for the
time being this is detemined by the meter. But I have
a case, where I would like to have a beem over maximally 
2 8th (or 4 16th, i.e. the equivalent of a 4th note)
in a piece using 4/4 meter?

thanks for any hint
Johannes