本人在学excel金融建模，下面的代码是调用规划求解，求解有卖空限制的有效投资组合，但是运行时，会出现：Range作用于对象'Global‘时失败，新手不懂，求高人指点呀
Option Explicit
Sub Solve()
    SolverOk SetCell:="$b$27", MaxMinVal:=1, ValueOf:="0", ByChange:="$b$19:$b$22"
    SloverSolve UserFinish:=True
End Sub
Sub doit()
    Dim counter
    Range("Results").ClearContents
    For counter = 1 To 40
        Range("constant") = -0.04 + counter * 0.005
        Solve
        Application.SendKeys ("{Enter}")
        Range("Result").Cells(counter, 1) = ActiveSheet.Range("constant")
        Range("Result").Cells(counter, 2) = ActiveSheet.Range("portfolio_sigma")
        Range("Result").Cells(counter, 3) = ActiveSheet.Range("portfolio_mean")
        Range("Result").Cells(counter, 4) = ActiveSheet.Range("x_1")
        Range("Result").Cells(counter, 5) = ActiveSheet.Range("x_2")
        Range("Result").Cells(counter, 6) = ActiveSheet.Range("x_3")
        Range("Result").Cells(counter, 7) = ActiveSheet.Range("x_4")
    Next counter
End Sub