程序代码：

Option Explicit

Private Declare Function MoveWindow Lib "user32" (ByVal hWnd As Long, ByVal x As Long, ByVal y As Long, ByVal nWidth As Long, ByVal nHeight As Long, ByVal bRepaint As Long) As Long
Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hWnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long
Private Const CB_GETITEMHEIGHT = &H154

Private Sub Combo1_GotFocus()
    SetComboHeight Combo1, 50
End Sub

Private Sub Form_Load()
    Dim i&
    For i = 0 To 333
        Combo1.AddItem i
    Next
End Sub

Private Sub SetComboHeight(cboNegPressureList As ComboBox, ByVal nListCount As Long)
Dim ListHeight As Long
With cboNegPressureList
    ListHeight = SendMessage(.hWnd, CB_GETITEMHEIGHT, 0,byval 0&)
    MoveWindow .hWnd, Me.ScaleX(.Left, Me.ScaleMode, vbPixels), Me.ScaleY(.Top, Me.ScaleMode, vbPixels), Me.ScaleX(.Width, Me.ScaleMode, vbPixels), ListHeight * nListCount, 1
End With
End Sub