vb做一个小程序，求助……

Private Sub Form_Load()
Dim year_i As Integer
Dim month_i As Integer
Dim i As Integer
Dim flag As Boolean
Dim day(1 To 12) As Integer
Dim j As Integer
For i = 1990 To 2009
Combo1.AddItem i
Next i
For i = 1 To 12
Combo2.AddItem i
Next i
year_i = Combo1.ListIndex + 1990
month_i = Combo2.ListIndex + 1
If (year_i Mod 4 = 0 And year_i Mod 100 <> 0) Or (year_i Mod 400 = 0) Then
day(1) = 31
day(2) = 28
day(3) = 31
day(4) = 30
day(5) = 31
day(6) = 30
day(7) = 31
day(8) = 31
day(9) = 30
day(10) = 31
day(11) = 30
day(12) = 31
For i = 1 To day(month_i)
Combo3.AddItem i
Next i
End If

End Sub

Dim year_i As Integer
Dim day(1 To 12) As Integer
Dim month_i As Integer
Dim i As Integer
Private Sub Combo2_click()
If (year_i Mod 4 = 0 And year_i Mod 100 <> 0) Or (year_i Mod 400 = 0) Then
year_i = Combo1.ListIndex + 1990
month_i = Combo2.ListIndex + 1
day(1) = 31
day(2) = 28
day(3) = 31
day(4) = 30
day(5) = 31
day(6) = 30
day(7) = 31
day(8) = 31
day(9) = 30
day(10) = 31
day(11) = 30
day(12) = 31
Debug.Print month_i
For i = 1 To day(month_i)
Combo3.AddItem i
Next i
End If
End Sub

Private Sub Form_Load()
Dim j As Integer
For i = 1990 To 2009
Combo1.AddItem i
Next i
For i = 1 To 12
Combo2.AddItem i
Next i
End Sub