您需要使用的方法如下所述：https://stackoverflow.com/a/8986622/9852011，但对于您的特定情况，您需要执行以下操作：

这是应该在用户窗体模块中的代码：

Private m_oCollectionOfEventHandlers As Collection

Private Sub UserForm_Initialize()
    Set m_oCollectionOfEventHandlers = New Collection
End Sub

Private Sub CommandButton1_Click()
    Dim ComboBox1 As MSForms.ComboBox
    Set ComboBox1 = Me.Controls.Add("Forms.ComboBox.1")
    With ComboBox1
        .Left = 160
        .Top = 50
        .Width = 70
        .Height = 20
        .AddItem ("> than")
        .AddItem ("< than")
        .AddItem ("Max")
        .AddItem ("Min")
        .Enabled = True
        .BackColor = RGB(255, 255, 255)
        .ForeColor = RGB(0, 0, 0)
        .SpecialEffect = fmSpecialEffectFlat
        .Font.Size = 12
        .Font.Bold = False
        .Font.Name = "Arial"
        .TabIndex = 2
    End With
        
    DoEvents
    ComboBox1.SetFocus
    
    Dim cb1EventHandler As comboboxeventhandler
    Set cb1EventHandler = New comboboxeventhandler
    Set cb1EventHandler.ComboBox = ComboBox1
    m_oCollectionOfEventHandlers.Add cb1EventHandler
      
End Sub

然后，在项目中插入一个新的类模块，将其命名为“ComboBoxEventHandler”，并将以下代码放入其中：

Private WithEvents m_oComboBox As MSForms.ComboBox

Public Property Set ComboBox(ByVal oComboBox As MSForms.ComboBox)
    Set m_oComboBox = oComboBox
End Property

Private Sub m_oComboBox_Change()
    Dim inputNumber As Variant
    With m_oComboBox
        If .Value = "> than" Then
            inputNumber = InputBox("Enter a number:")
            'Check if the input is valid number
            If IsNumeric(inputNumber) Then
                .Value = .Parent.ComboBox2.Value & " " & inputNumber
            Else
                MsgBox "Invalid input"
            End If
        End If
    End With
End Sub

我不知道“ComboBox2”是什么，但是为了这个例子，我假设它是一个已经存在于UserForm中的ComboBox。