求大神改善三链数法代码

lingyuncelia1

本人想写一个数独的三链数法代码。
在前9个单元格中，红色数字是候选数，候选数是大于一位的，每个格的红色数的数字绝不重复（如B1:157，绝对不会出现155之类），且是升序排列的（如B1:157，绝对不会是175或751之类）。如果我们发现前9格有三个格子只使用了三个候选数（肉眼发现是457），那么这三个格子（最后3格的数字全部包含于K1内的457）必然正好是这三个数字，那么在这9格中，其它格子不会出现这三个候选数（因此B1的数字5与7去掉，F1的4去掉），这就是三链数法。
如上图，运行以下代码，变右图：
Sub ba()
Dim reg, s As Range, m, n As Integer
Set reg = CreateObject("vbscript.regexp")
With reg
    .Global = True
    .Pattern = "[" & [k1] & "]"
    For Each s In Range("a1:i1")
        Set m = .Execute(s.Value)
        If Len(s) = 3 And m.Count = 3 Then s.Font.Size = 36
        If Len(s) = 2 And m.Count = 2 Then s.Font.Size = 36
        If s.Font.Size = 36 Then n = n + 1
    Next
End With
Set reg = Nothing
If n = 3 Then
a = Mid(Cells(1, 11).Text, 1, 1)
b = Mid(Cells(1, 11).Text, 2, 1)
c = Mid(Cells(1, 11).Text, 3, 1)
For Each s In Range("a1:i1")
  If s.Font.Size = 11 Then s.Value = Replace(s.Text, a, ""): s.Value = Replace(s.Text, b, ""): s.Value = Replace(s.Text, c, "")
Next
Else
For Each s In Range("a1:i1")
If s.Font.Size = 36 Then s.Font.Size = 11
Next
End If
End Sub

但是，如果将代码改成以下这样则无效，为什么呢？

Sub ba()
Dim reg, s As Range, m, n As Integer
For a = 1 To 7
For b = a + 1 To 8
  For c = b + 1 To 9
Set reg = CreateObject("vbscript.regexp")
With reg
    .Global = True
    .Pattern = "[a & b & c]"
    For Each s In Range("a1:i1")
        Set m = .Execute(s.Value)
        If Len(s) = 3 And m.Count = 3 Then s.Font.Size = 36
        If Len(s) = 2 And m.Count = 2 Then s.Font.Size = 36
        If s.Font.Size = 36 Then n = n + 1
    Next
End With
Set reg = Nothing
If n = 3 Then
For Each s In Range("a1:i1")
  If s.Font.Size = 11 Then s.Value = Replace(s.Text, a, ""): s.Value = Replace(s.Text, b, ""): s.Value = Replace(s.Text, c, "")
Next
Else
For Each s In Range("a1:i1")
If s.Font.Size = 36 Then s.Font.Size = 11
Next
End If
  Next c
Next b
Next a
End Sub