Max, nice idea.

However, since I already had the following implementation ready to post, I'll do that too. Thought of this more as a fun challenge

Here we are going to do most stuff by API. We will avoid the Unicode to ANSI conversion for each string added to the combobox and by also including the WM_SETREDRAW message, this screams
Code:
Private Declare Function SendMessage Lib "user32.dll" Alias "SendMessageA" (ByVal hWnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByRef lParam As Any) As Long
Private Const WM_SETREDRAW As Long = &HB
Private Const CB_ADDSTRING As Long = &H143


Private Sub Form_Load()


    Dim intN As Integer
    Dim intM As Integer
    Dim arrItems(0 To 4) As Byte
    Dim intO As Integer
    
    Dim sPtr As Long
    sPtr = VarPtr(arrItems(0))
    
    For intN = 0 To 31
        Combo1(intN).Clear
        Erase arrItems()
        
        SendMessage Combo1(intN).hWnd, WM_SETREDRAW, 0&, ByVal 0&
        
' do 1-9
        For intM = 49 To 57 ' 1-9
            arrItems(0) = intM
            SendMessage Combo1(intN).hWnd, CB_ADDSTRING, 0&, ByVal sPtr
        Next
' do 10-99
        For intO = 49 To 57
            arrItems(0) = intO ' tens
            For intM = 48 To 57 ' 0-9
                arrItems(1) = intM
                SendMessage Combo1(intN).hWnd, CB_ADDSTRING, 0&, ByVal sPtr
            Next
        Next
' do 100-199
        arrItems(0) = 49 ' 100 place
        For intO = 48 To 57 ' 0-9 tens
            arrItems(1) = intO
            For intM = 48 To 57 ' 0-9
                arrItems(2) = intM
                SendMessage Combo1(intN).hWnd, CB_ADDSTRING, 0&, ByVal sPtr
            Next
        Next
' do 200-249
        arrItems(0) = 50 ' 200 place
        For intO = 48 To 52 ' 0-4 tens
            arrItems(1) = intO
            For intM = 48 To 57 ' 0-9
                arrItems(2) = intM
                SendMessage Combo1(intN).hWnd, CB_ADDSTRING, 0&, ByVal sPtr
            Next
        Next
' do 250-256
        arrItems(1) = 53 ' 50 place
        For intM = 48 To 54 ' 0-6
            arrItems(2) = intM
            SendMessage Combo1(intN).hWnd, CB_ADDSTRING, 0&, ByVal sPtr
        Next

        Combo1(intN).ListIndex = 0
        
        SendMessage Combo1(intN).hWnd, WM_SETREDRAW, 1&, ByVal 0&
    Next
    
End Sub
The loops are using ASCII values of 0 thru 9, vs decimal values of 0 thru 9