List numbering problem

I am trying to do the following type of list:

a.  Step

b.  Step

c.  Step

    1. Sub step

    2. Sub step

d.  Step

I am controlling the numbering in the EDD.  My problem is that step d defaults to 'c' instead of d and I have to manually change it from <a+>.\t  to  <a=4>.\t.   Steps 1 and 2 are set to <n=1>.\t and <n+>.\t.  So why doesn't the next alpha list pick up on the last alpha list instead of the last numeric list?  Is there any way to fix this?  Thanks!  JW