Value retrieval from the multiple selection dropdown in Excel

Question

I am trying to make calculation from my dropdown menu. I have following dropdown in sheet 1 in my Excel.

## Category ##
### AAA ###
### BBB ###
### CCC ###
### DDD ###

In sheet 2, I have corresponding values for this dropdown.

## Category  Category Value##
### AAA    1###
### BBB    2###
### CCC    3###
### DDD    4###

I added VBA code for multiple selection and also added simple VLOOKUP formula to retrieve the value of category.

=VLOOKUP(E2;Sheet2!I2:J5;2;)

With the VBA code, I am able to select all three category and also remove the selected category later. But I am failing to retrieve the sum of selected category. E.g., if a customer chooses category AAA & CCC, he/she should be able to see sum as 4. Also, if a customer first chooses all three categories and then removes one of them, then the sum should get updated. I am not getting how do I update my VLOOKUP formula to get the sum.

Here is my VBA code for multiple selection.

Private Sub Worksheet_Change(ByVal Target As Range)
    'Updated: 2016/4/12
    Dim xRng As Range
    Dim xValue1 As String
    Dim xValue2 As String
    If Target.Count > 1 Then Exit Sub
    On Error Resume Next
    Set xRng = Cells.SpecialCells(xlCellTypeAllValidation)
    If xRng Is Nothing Then Exit Sub
    Application.EnableEvents = False
    If Not Application.Intersect(Target, xRng) Is Nothing Then
        xValue2 = Target.Value
        Application.Undo
        xValue1 = Target.Value
        Target.Value = xValue2
        If xValue1 <> "" Then
            If xValue2 <> "" Then
                '                If xValue1 = xValue2 Or _
                '                   InStr(1, xValue1, ", " & xValue2) Or _
                InStr(1, xValue1, xValue2 & ",") Then
                If InStr(1, xValue1, xValue2 & ",") > 0 Then
                    xValue1 = Replace(xValue1, xValue2 & ", ", "") ' If it's in the middle with comma
                    Target.Value = xValue1
                    GoTo jumpOut
                End If
                If InStr(1, xValue1, ", " & xValue2) > 0 Then
                    xValue1 = Replace(xValue1, ", " & xValue2, "") ' If it's at the end with a comma in front of it
                    Target.Value = xValue1
                    GoTo jumpOut
                End If
                If xValue1 = xValue2 Then        ' If it is the only item in string
                    xValue1 = ""
                    Target.Value = xValue1
                    GoTo jumpOut
                End If
                Target.Value = xValue1 & ", " & xValue2
            End If
            jumpOut:
        End If
    End If
    Application.EnableEvents = True
End Sub

Answer 1

=SUM(IF(ISERR(FIND(Sheet2!$I$2:$I$5;A1;1));0;Sheet2!$J$2:$J$5))

This must work, but it is not a regular formula. It is an array formula. For array formulas to work, you enter it not with Enter, but instead use a combination of Ctrl+Shift+Enter.

Also, change the A1 to your actual dropdown cell.