Using vba to populate ComboBox list using named ranges

Try this. It assumes each named range is based on the OD letter using this naming convention:
OD_A
OD_B
OD_C
...etc

It gets the OD letter of the selected item from the second column of cboOD

Private Sub cboOD_Change()
    
    Dim v As Variant, i As Long
    
    If Me.cboOD.ListIndex = -1 Then Exit Sub
    
    v = Sheets(1).Range("OD_" & Me.cboOD.List(Me.cboOD.ListIndex, 1))
    
    With cboWt
        .Clear
        .ColumnCount = 3
        .ColumnWidths = ";0;0"
        For i = 1 To UBound(v, 1)
            .AddItem v(i, 2)
            .List(.ListCount - 1, 1) = v(i, 3)
            .List(.ListCount - 1, 2) = v(i, 4)
        Next i
    End With
    
End Sub