Beaming

[Norman Humphrys]

Hi 

I am writing a score for a 3-part Bach Fugue, with parts for clarinet, euphonium and piano. The notation is mainly in quavers and semiquaver groups. The default beaming joins all the notes together in a 3/4 bar: so 12 semiquavers are all beamed together; a quaver followed by 10 semiquavers all beamed together; a quaver, six semiquavers plus two quavers all beamed together. I want to beam all semiquavers in crotchet groups of four, so we can see the beat easily; and quaver followed by two semiquavers in one beam, for the same reason - to see the quarter-note beat. 

How do I get control of the beams? 

Thanks  

Norman