I have a list box (extended multi-select) that contains a list of possible variables that I can plot in Excel. The listbox contains only the variable names which will be found in the header row of my Excel worksheet. I want to select one or more variables from the listbox and plot the selected data.

I can manually set the range as shown in red below and the plot is generated as I want. The problem that I'm having is trying to set this range based on the listbox selection. I can get a numeric value that represents the column that I want but how do I get the A:A syntax? Do I need this format?

Code:
        Dim oCht As Excel.Chart
        Dim oSht As Excel.Worksheet
        Dim oWB As Excel.Workbook
        Dim oRng As Excel.Range
        Dim strRng As String = "A:A" 'The first column (time) will always be used

        Try
            oApp = New Excel.Application
            oWB = oApp.Workbooks.Open("c:\temp\test.xls")
            oSht = CType(oApp.Worksheets(1), Excel.Worksheet)
            oCht = CType(oWB.Charts.Add, Excel.Chart)

            'For Each idx As Integer In lstAllVars.SelectedIndices
            '    strRng = lstAllVars.Items(idx).ToString
            '    oRng = CType(oSht.Cells(1, idx), Excel.Range).EntireColumn
            'Next
            oRng = oSht.Range("A:A,B:B,D:D")

            With oCht
                .SetSourceData(oRng)
                .Name = "MyChartTab"
                .PlotBy = Excel.XlRowCol.xlColumns
                .HasTitle = True
                .ChartTitle.Text = "MyChart"
            End With

            oApp.Visible = True

        Catch ex As Exception
            MessageBox.Show(ex.Message.ToString)
        End Try