Don't use Select or Selection, just attach the sort  directly to the range.
And try "A2" instead of "A2:B8" to allow Excel to select the range
dynamically.

To get the auto  sort, you will need to call the subroutine from the
Worksheet's Change event. To stop it happening on every worksheet change,
you'll need to limit it to changes to the B column. The If statement you
want for this is:

If (Not Intersect(Target, Columns("B")) Is Nothing) Then
Call SortAsc
End If

It's fun to try, but I bet you turn it off pretty quickly. :-)