Sure, I can help you with that! Here's a step-by-step guide on how to change the point size of all points in an XY chart using VBA:

1. Open your Excel workbook and press Alt + F11 to open the Visual Basic Editor.
2. In the Project Explorer window, find the worksheet that contains the XY chart you want to modify and double-click on it to open the code window.
3. Click on the "Insert" menu and select "Module" to create a new module.
4. In the new module, paste the following code:
   
   
   Formula:

   Sub ChangePointSize()
    Dim cht As ChartObject
    Dim ser As Series
    
    For Each cht In ActiveSheet.ChartObjects
        For Each ser In cht.Chart.SeriesCollection
            ser.MarkerSize = 2
        Next ser
    Next cht
End Sub 

5. Press F5 or click on the "Run" button to execute the code.
6. The code will loop through all the chart objects in the active worksheet and change the marker size of all series to 2.

That's it! The point size of all points in your XY chart should now be reduced to 2. If you want to change the point size to a different value, simply modify the number in the "ser.MarkerSize = " line of the code.