使用vba为excel文字添加下划线

Sub city()
Dim a As String
Dim b1 As String
Dim b2 As String
Dim b3 As String
For i = 2 To 45
For j = 2 To 13
a = Worksheets("city").Cells(i, j)
b1 = Mid(a, 1, 1)
If (b1 = "b" Or b1 = "A" Or b1 = "B" Or b1 = "C") Then
b2 = Mid(a, 2, 1)
If (b2 = "b" Or b2 = "A" Or b2 = "B" Or b2 = "C") Then
b3 = Mid(a, 3, 1)
If (b3 = "b" Or b3 = "A" Or b3 = "B" Or b3 = "C") Then
Worksheets("city").Cells(i, j).Characters(1, 3).Font.Underline = xlUnderlineStyleSingle

End If
End If
End If

Next j
Next i

End Sub