Does the query parse out okay (you know, if you hit the check box icon)?

It's just like Julie said:

Declare @BeginDate varchar(8)

Declare @EndDate varchar(8)

Select @BeginDate = convert(varchar,DateAdd(mm, DateDiff(mm, 0, dateadd(mm, -2, Getdate())),0),112)

Select @EndDate = convert(varchar,DateAdd(mm, DateDiff(mm, 0, dateadd(mm, -1, Getdate())),0),112)

You've gotta declare and set those...