I put your data in A2:A6, and in B2 put this formula:
=LEFT(A2,FIND("-",A2)-1)&TEXT(MID(A2,FIND("-",A2)+1,100),"0000000000")
I copied that down as need, and then sorted using that column. Worked pretty well :)
Now let me ask you, how should these sort:
01/19/2009-1
01/19/2009-10
01/19/2009-6
01/19/2009-8
01/19/2009-9
02/19/2008-1
02/19/2008-10
02/19/2008-6
02/19/2008-8
02/19/2008-9