r(3).s = "  " & a.s & " * " & b.s & "  "

        r(4).s = "  " & a.s & " / " & b.s & "  "

程序代码：

Option Explicit

Public Type T24type
    s As String
    v As Long
End Type

Public Function Test24_2(a As Long, b As Long, c As Long, d As Long) As String

Dim r1(4) As T24type, r2(4) As T24type, r3(4) As T24type
Dim l1 As T24type, l2 As T24type
Dim l3 As T24type, l4 As T24type
Dim i As Long, j As Long, m As Long
Dim s As String

'第一个数
l1.s = CStr(a)
l1.v = a
'第二个数
l2.s = CStr(b)
l2.v = b
'第三个数
l3.s = CStr(c)
l3.v = c
'第四个数
l4.s = CStr(d)
l4.v = d

'第一个数与第二个数计算
Call operation(l1, l2, r1)

'第一分支，第1、2数运算后与第3、4数运算

'第三个数与第四个数计算
Call operation(l3, l4, r2)
For i = 1 To 4
    If r1(i).v > 0 Then
        For j = 1 To 4
            If r2(j).v >= 0 Then
                Call operation(r1(i), r2(j), r3)
                For m = 1 To 4
                    If r3(m).v = 24 Then
                        s = s & r3(m).s & " = 24" & vbCrLf
                    End If
                Next m
            End If
        Next j
    End If
Next i

'第二分支，第1、2数运算后与第3数运算,再与第4数运算
For i = 1 To 4
    If r1(i).v >= 0 Then
        Call operation(r1(i), l3, r2)
        For j = 1 To 4
            If r2(j).v >= 0 Then
                Call operation(r2(j), l4, r3)
                For m = 1 To 4
                    If r3(m).v = 24 Then
                        s = s & r3(m).s & " = 24" & vbCrLf
                    End If
                Next m
            End If
        Next j
    End If
Next i

'先第2、3数运算后，再与第1数运算，第4数运算。
Call operation(l2, l3, r1)
For i = 1 To 4
    If r1(i).v > 0 Then
        Call operation(l1, r1(i), r2)
        For j = 1 To 4
            If r2(j).v > 0 Then
                Call operation(r2(j), l4, r3)
                For m = 1 To 4
                    If r3(m).v = 24 Then
                        s = s & r3(m).s & " = 24" & vbCrLf
                    End If
                Next m
            End If
        Next j
    End If
Next i


'去掉括号之间的空格
s = Replace(s, "( (", "((")
'去多余的空格
Do
    i = Len(s)
    s = Replace(s, "  ", " ")
Loop While Len(s) <> i

'去重
Dim fj() As String
'分行
fj = Split(s, vbCrLf)

'扫描
For i = 1 To UBound(fj)
    For j = i + 1 To UBound(fj)
        If fj(i) = fj(j) Then       '扫描到后面有相同的
            fj(j) = ""              '后面的清空
        End If
    Next j
Next i
'重新组合，不能使用 join 函数是因为有空行在
s = ""
For i = 0 To UBound(fj)
    If Len(fj(i)) > 0 Then
        s = s & fj(i) & vbCrLf
    End If
Next i

Test24_2 = s

End Function

Public Sub operation(a As T24type, b As T24type, r() As T24type)

Dim t As Single

'加法
r(1).v = a.v + b.v
r(1).s = "( " & a.s & " + " & b.s & " )"

'减法，不考虑负数
If a.v > b.v Then
    r(2).v = a.v - b.v
    r(2).s = "( " & a.s & " - " & b.s & " )"
Else
    r(2).v = -1
End If

'乘法
r(3).v = a.v * b.v
'r(3).s = "( " & a.s & " * " & b.s & " )"
r(3).s = "  " & a.s & " * " & b.s & "  "

'除法，只允许整除
If a.v >= b.v And b.v > 0 Then
    If a.v Mod b.v = 0 Then
        r(4).v = a.v / b.v
'        r(4).s = "( " & a.s & " / " & b.s & " )"
        r(4).s = "  " & a.s & " / " & b.s & "  "
    Else
        r(4).v = -1
    End If
    
Else
    r(4).v = -1
End If

End Sub