Code:
sub M_snb()
  sn=sheets(1).cells(1).currentregion.resize(,3)

  for j=2 to ubound(sn)
    sn(j,2)=sn(j,3)
    if lcase(left(sn(j,1),3))="ext" then sn(j,2)=""
  next
  sheets(1).cells(1).currentregion.resize(,3)=sn

  for each it in sheets(1).cells(1).currentregion.columns(2).specialcells(4)
     it.offset(,1).copy it
  next
End Sub