how write any character (greek, unit, ...) in text mode inside a formula

[Pierrick Mellerin]

Hello,

I use LyX-1.2.0cvs and I would like to know how can I write any greek 
character in text mode ? And what must I do for writing any character like 
unit (m, kg, ..) in text mode inside a formula ? For example, I have to write 
the following sentence : "0,4 um < l < 0,8 um", where u is mu, l is lambda 
and m is for meter. The problem is that u, m and l are in math mode and so 
they are displayed and printed in italics ...

Thanks in advance and best regards,

Pierrick.