substring

["Cadenas, Maria (MT)" <MCadenas@DOW.COM>]

we need to select the first six letters of a last name for each employee,
however, the format for the field is:
Last, First Middle (i.e. Lee, James G)

Is there a way to make sure we substring only the first six letters of ONLY
the last name? so that if the last name is three digits (i.e Lee) we ONLY
get Lee and NOT Lee, J?

Any advice is appreciated.