早些时候我遇到了一个问题，即求解器没有通过 VBA 向模型添加二进制约束……我（大部分）已经解决了这个问题。但现在我有一个新问题。首先，让我发布违规代码的相关部分。我应该注意到这是在 Excel 2007 中运行的。
'build string of ByChange cells and set up cascading constraints
by_change_string = ""
For i = 1 To j - 1
If Len(by_change_string) > 0 Then 'there are already some elements in the string, so we might start with a comma
If Not (Right(by_change_string, 1) = ",") Then 'make sure the last character isn't already a comma
by_change_string = by_change_string & ","
End If
End If
current_status = Sheets("Buyback Risk Area").Range("C1").Offset(i).Value
Select Case current_status
Case "Y" 'risk area is currently yellow, so green transition is available
by_change_string = by_change_string & "$E$" & i + 1
solverok setcell:="$B$" & j + 4, MaxMinVal:=2, ValueOf:="0", ByChange:=by_change_string
'add binary constraints
solveradd cellref:="$E$" & i + 1, relation:=5, formulatext:="binary"
Case "O" 'risk area is currently orange, so green and yellow transitions are available
by_change_string = by_change_string & "$E$" & i + 1 & ",$G$" & i + 1
solverok setcell:="$B$" & j + 4, MaxMinVal:=2, ValueOf:="0", ByChange:=by_change_string
'add cascading constraints
solveradd cellref:="$E$" & i + 1, relation:=1, formulatext:="$G$" & i + 1 'says E <= G, which means you can't select green unless you've already selected yellow
'add binary constraints
solveradd cellref:="$E$" & i + 1, relation:=5, formulatext:="binary"' solveradd cellref:="$G$" & i + 1, relation:=5, formulatext:="binary"
Case "R" 'risk area is currently red, so green, yellow, and orange transitions are available
by_change_string = by_change_string & "$E$" & i + 1 & ",$G$" & i + 1 & ",$I$" & i + 1
'solverok setcell:="$B$" & j + 4, MaxMinVal:=2, ValueOf:="0", ByChange:=by_change_string
'add cascading constraints
solveradd cellref:="$E$" & i + 1, relation:=1, formulatext:="$G$" & i + 1 'says E <= G, which means you can't select green unless you've already selected yellow
solveradd cellref:="$G$" & i + 1, relation:=1, formulatext:="$I$" & i + 1 'says G <= I, which means you can't select yellow unless you've already selected orange
'add binary constraints
solveradd cellref:="$E$" & i + 1, relation:=5, formulatext:="binary"
solveradd cellref:="$G$" & i + 1, relation:=5, formulatext:="binary"
solveradd cellref:="$I$" & i + 1, relation:=5, formulatext:="binary"
Case "B" 'risk area is black, so green, yellow, orange and red transitions are avaailable
by_change_string = by_change_string & "$E$" & i + 1 & ",$G$" & i + 1 & ",$I$" & i + 1 & ",$K$" & i + 1
solverok setcell:="$B$" & j + 4, MaxMinVal:=2, ValueOf:="0", ByChange:=by_change_string
'add cascading constraints
solveradd cellref:="$E$" & i + 1, relation:=1, formulatext:="$G$" & i + 1 'says E <= G, which means you can't select green unless you've already selected yellow
solveradd cellref:="$G$" & i + 1, relation:=1, formulatext:="$I$" & i + 1 'says G <= I, which means you can't select yellow unless you've already selected orange
solveradd cellref:="$I$" & i + 1, relation:=1, formulatext:="$K$" & i + 1 'says K <= M, which means you can't select orange unless you've already selected red
'add binary constraints
solveradd cellref:="$E$" & i + 1, relation:=5, formulatext:="binary"
solveradd cellref:="$G$" & i + 1, relation:=5, formulatext:="binary"
solveradd cellref:="$I$" & i + 1, relation:=5, formulatext:="binary"
solveradd cellref:="$K$" & i + 1, relation:=5, formulatext:="binary"
End Select
Next i
'buyback amount constraint
solveradd cellref:="$O$" & j + 1, relation:=1, formulatext:="$B$" & j + 2
'set target cell
solverok setcell:="$B$" & j + 4, MaxMinVal:=2, ValueOf:="0", ByChange:=by_change_string
'set binary constraints
'binary_array = Split(by_change_string, ",")
'For i = 0 To UBound(binary_array)
' solveradd cellref:=Range(binary_array(i)), relation:=5, formulatext:="binary"
'Next i
Application.ScreenUpdating = True
SolverSolve userFinish:=False
这里的基本思想是遍历工作表并查看数据（从执行到执行会发生变化）并构建适当的模型。
字符串 by_change_string 包含所有变化变量的单元格地址，它们都是二进制的。因此，当代码检查电子表格的每一行时，它会确定该行上的哪些单元格可供模型考虑，并将它们附加到字符串中。
使用不断增长的 by_change_string 多次调用 solverok 是为了解决未将二元约束添加到模型中的早期问题。所有 <= 约束都是，但不是二进制约束。在将变量添加到模型之前，您似乎无法将其约束为二进制。在构造 by_change_string 的循环完成后，曾经只有一个 solverok 语句，但是当我这样做时，我得到了所有的 <= 约束并且没有二进制约束。
当这段代码在我的测试表上运行时，生成的模型应该有 136 个决策变量（通过更改单元格）。我查过了，by_change_string 实际上有 136 个地址。但是当我查看求解器对话框时，只有前 41 个。我在调试模式下逐步执行了整个执行过程，并看到它在每次迭代后调用 solverok，但由于某种原因，只有前 41 个由更改单元格存在. 并且出现问题的那一行数据并没有什么特别之处……这不像是某个选定案例的第一个实例或其他什么……
当求解器在这个简化模型上运行时，它会返回一个它认为是最优的垃圾解决方案。基本上它保持一切相同，因此最终的目标函数值与起始值相同。
所以然后我尝试了其他东西......你会注意到底部有一个注释掉的代码块：
'set binary constraints
'binary_array = Split(by_change_string, ",")
'For i = 0 To UBound(binary_array)
' solveradd cellref:=Range(binary_array(i)), relation:=5, formulatext:="binary"
'Next i
这里的想法是通过将所有这些 solverok 和 solveradd 语句从选择案例中取出来使事情变得更加高效。通过等到最后的solverok语句之后，所有变量现在都在模型中，所以你应该只需要逐步执行by_change_string并将每个变量都设为二进制变量。这样，您只需要一个solverok 语句，您就可以摆脱选择案例中的所有solveradd 语句。所以我在选择的情况下注释掉了所有这些solverok和solveradd，然后再次运行宏。我没有得到求解器的输出。当我在运行后查看求解器对话框时，目标单元格和通过更改单元格字段都是空白的。就好像最后一个solverok语句从未运行过。
所以然后我尝试取消所有solverok的注释，但将solveradd的二进制变量注释掉。我回到只获取前 41 个决策变量。设置二进制约束的循环完成了它的工作，但是solveradd没有将变量放入模型中。
在这一点上，我非常难过。有任何想法吗？