Office 2021 won't let my assign data cells to an excel bar chart x-axis

I've expanded the ExcelHelper class from my last answer[^] to help with this answer:

public class ExcelHelper
{
    public ExcelHelper(string path)
    {
        _path = path;
        _workbook = _excel.Workbooks.Open(path);

        _excel.DisplayAlerts = false;
    }

    private readonly string _path;

    private readonly _Application _excel = new _Excel.Application();

    private readonly Workbook _workbook;

    public IEnumerable<Worksheet> Worksheets()
    {
        foreach (Worksheet worksheet
                           in _workbook.Worksheets
                                       .Cast<Worksheet>())
            yield return worksheet;
    }

    public IEnumerable<Chart> GetCharts(Worksheet worksheet)
    {
        foreach (var chartObject
                     in worksheet.ChartObjects())
            yield return chartObject.Chart;
    }

    public Worksheet Worksheet(string name)
    {
        return (Worksheet)_workbook.Worksheets[name];
    }

    public ChartObject ChartObject(Worksheet worksheet, string ChartName)
    {
        return (ChartObject)worksheet.ChartObjects(ChartName);
    }

    public void SaveChanges()
    {
        _workbook.SaveAs(Filename: _path,
                         AccessMode: XlSaveAsAccessMode.xlNoChange);
    }

    public void Close(bool Save = false)
    {
        if (save)
            SaveChanges();

       // no longer required
        _workbook.Close();
    }
}

Here I have added methods Worksheet, ChartObject, and SaveChanges to help simplify common tasks.

Now to work with the chart object to set the data source:

string resourcePath = Path.Combine(Environment.CurrentDirectory, "Workbooks");
string path = Path.Combine(resourcePath, "Book1.xlsx");

ExcelHelper excelHelper = new ExcelHelper(path);

Worksheet worksheet = excelHelper.Worksheet("MySheet");
ChartObject chartObject = excelHelper.ChartObject(worksheet, "MyChart");
Chart myChart = chartObject.Chart;

// Data is already on the same worksheet as the chart
_Excel.Range ChartSourceRange = worksheet.Range["B22", "E25"];

// Set the Chart data
myChart.SetSourceData(ChartSourceRange);

// Set the Chart Type
myChart.ChartType = XlChartType.xlColumnClustered;

// lets save an image of the Chart to file
//   so we can check what it looks like
myChart.Export(Path.Combine(resourcePath, "MyChart.bmp"), "BMP");

// We're done, so save changes
excelHelper.SaveChanges();

// Close the workbook
excelHelper.Close();

Tested and works. Enjoy...

PS: I should point out that you are working with COM objects, so you will need to release them. I would use an IDisposable interface on the ExcelHelper, but I will leave that up to you. You can read more here: Working with COM in .Net requires to release com objects - Stack Overflow[^]