Excel-VBA update userform listbox based on existing list - excel

Question

I have a useform with multicolumn listbox which lists items and its quantity. The intent is to be able to dynamically update the quantity by adding or deducting from a textbox input. Below is my current code roughly to realize this. So far it is not working with invalid qualifier error for selected(i). would appreciate any guidance on this
Private Sub CB_AddOrder_Click()
Dim j, k, qty As Integer
Dim i As Variant
qty = TB_Qty.Value
If qty = 0 Then
Exit Sub
End If
j = LB_Order.ListCount - 1
Debug.Print j
If j < 0 Then
j = 0
End If
'Iterate to check if selected menu already existed in ordered list
For i = 0 To LB_Menu.ListCount - 1
If LB_Menu.Selected(i) = True Then
Debug.Print Selected(i)
For k = 0 To j
If LB_Menu.Selected(i).List(i, 0) = LB_Order.List(k, 0) Then
LB_Order.List(k, 3) = LB_Order.List(k, 3).Value + qty
Exit Sub
End If
Next k
With LB_Order
.ColumnCount = 5
.ColumnWidths = "120;60;60;60;60"
.AddItem
.List(j, 0) = LB_Menu.List(i, 0)
.List(j, 1) = LB_Menu.List(i, 1)
.List(j, 2) = LB_Menu.List(i, 2)
.List(j, 3) = qty
.List(j, 4) = Format(qty * LB_Menu.List(i, 2), "0.00")
End With
End If
Next i
End sub

Answer 1

The confusion you're having relates from the difference in which listbox item(s) are selected and the value of those selected item(s). So when you check for Selected:
Dim i As Long
For i = 0 To LB_Menu.ListCount - 1
If LB_Menu.Selected(i) Then
Debug.Print "Menu selected (" & i & ") = " & LB_Menu.List(i, 0)
End If
Next i
Once you determine which index (i in this case) is selected, you refer to the value by using the index into the List.
The Object Required error you received is because your statement
LB_Order.List(k, 3) = LB_Order.List(k, 3).Value + qty
is using .Value for the list item. This item is a value, not an object.
Here is your sub rewritten as an example. Notice that I'm using single-character variables as loop indexes (which is good), but not as a meaningful value. I renamed other variables in (a hopefully) meaningful way to make your code a little more self-documenting.
Option Explicit
Private Sub CB_AddOrder_Click()
Dim additionalQty As Long
additionalQty = TB_Qty.Value
If additionalQty = 0 Then
Exit Sub
End If
Dim countOfOrderItems As Long
countOfOrderItems = LB_Order.ListCount - 1
If countOfOrderItems < 0 Then
countOfOrderItems = 0
End If
'Iterate to check if selected menu already existed in ordered list
Dim i As Long
For i = 0 To LB_Menu.ListCount - 1
If LB_Menu.Selected(i) Then
Debug.Print "Menu selected (" & i & ") = " & LB_Menu.List(i, 0)
'--- find the matching item and increase the quantity
Dim k As Long
For k = 0 To countOfOrderItems
If LB_Menu.List(i) = LB_Order.List(k, 0) Then
LB_Order.List(k, 3) = LB_Order.List(k, 3) + additionalQty
Exit Sub
End If
Next k
'--- append the new item from the Menu to the Order
With LB_Order
.ColumnCount = 5
.ColumnWidths = "120;60;60;60;60"
.AddItem
.List(countOfOrderItems, 0) = LB_Menu.List(i, 0)
.List(countOfOrderItems, 1) = LB_Menu.List(i, 1)
.List(countOfOrderItems, 2) = LB_Menu.List(i, 2)
.List(countOfOrderItems, 3) = additionalQty
.List(countOfOrderItems, 4) = Format(additionalQty * LB_Menu.List(i, 2), "0.00")
End With
End If
Next i
End Sub
By the way, make sure all of the columns in your listboxes are initialized with values if you will add/subtract number values. If they are just Null, you'll get a Could not set the List property error.