VBA: Only add unique values to excel combobox, which is populated by looping through a source sheet range on workbook open - excel

Question

The below code basically looks at a source sheet on workbook open, takes the values from a range and loops through adding each value to a combobox.
What I want to do is include some code to ensure only unique values, i.e. no dupes, are added.
Any ideas how I can get that working?
Thanks!
Private Sub Workbook_Open()
Dim wb As Workbook
Set wb = ThisWorkbook
Dim Home As Worksheet
Dim Datasource As Worksheet
'Define Variables and dropdown object
Dim LastRow As Long
Dim MIDCell As Range
Dim ComboMID As ComboBox
Set Home = ActiveSheet
Set Home = Worksheets("UPDATER")
Set Datasource = wb.Sheets("LaunchCodes")
'asign dropdown object to combobox
Set ComboMID = Home.OLEObjects("ComboBox1").Object
'Empty the combobox currnetly to avoid duplicating content
ComboMID.Clear
'With and For loop to put all values in games launch code column, ignoring any blanks, into combobox
With Datasource
LastRow = .Cells(.Rows.Count, "D").End(xlUp).Row
For Each MIDCell In .Range("D2:D1000" & LastRow)
If MIDCell.Value <> "" Then
ComboMID.AddItem MIDCell.Value
End If
Next
End With
End Sub

Answer 1

The code below avoids looping through cells in a worksheet because it's slow. Actually, that process can be sped up by reading the list into a variable (as, in fact, my code also does) but using Excel's own RemoveDuplicates method appears more efficient.
Private Sub Workbook_Open()
' 155
Dim Wb As Workbook
Dim ComboMid As ComboBox
Dim TmpClm As Long ' number of temporary column
Dim Arr As Variant ' unique values from column D
Set Wb = ThisWorkbook
With Wb.Worksheets("UPDATER")
Set ComboMid = .OLEObjects("ComboBox1").Object
With .UsedRange
TmpClm = .Column + .Columns.Count
End With
End With
With Wb.Sheets("LaunchCodes")
' create a copy of your data (without header) in an unused column
.Cells(2, "D").CurrentRegion.Copy .Cells(1, TmpClm)
.Cells(1, TmpClm).CurrentRegion.RemoveDuplicates Columns:=1, Header:=xlNo
Arr = .Cells(1, TmpClm).CurrentRegion.Value
.Columns(TmpClm).ClearContents
End With
With ComboMid
.List = Arr
.ListIndex = 0 ' assign first list item to Value
End With
End Sub
You don't need to clear the combo box in the above code because replacing the List property with a new array automatically removes whatever it was before.

Answer 2

Unique to ComboBox
To learn about the combo box study this.
You can replace the code after the line Set ComboMID = Home.OLEObjects("ComboBox1").Object with the following snippet:
Dim rng As Range
With DataSource
LastRow = .Cells(.Rows.Count, "D").End(xlUp).Row
Set rng = .Range("D2:D" & lastrow)
End With
Dim Unique As Variant
Unique = getUniqueFromRange(rng)
If Not IsEmpty(Unique) Then
ComboMID.List = Unique
End If
which uses the following function:
Function getUniqueFromRange( _
rng As Range) _
As Variant
If rng Is Nothing Then
Exit Function
End If
Dim Data As Variant
If rng.Cells.CountLarge > 1 Then
Data = rng.Value
Else
ReDim Data(1 To 1, 1 To 1)
Data(1, 1) = rng.Value
End If
cCount = UBound(Data, 2)
Dim cValue As Variant
Dim i As Long
Dim j As Long
With CreateObject("Scripting.Dictionary")
.CompareMode = vbTextCompare
For i = 1 To UBound(Data, 1)
For j = 1 To cCount
cValue = Data(i, j)
If Not IsError(cValue) And Not IsEmpty(cValue) Then
.Item(cValue) = Empty
End If
Next j
Next i
If .Count > 0 Then
getUniqueFromRange = .Keys
End If
End With
End Function