You could try the scatter chart approach by inserting extra points on the X axis before and after each of the real data points.
m/z Absolute Intensity
The macro below will do the inserts if you have the m/z header in A1. You may need to make the lines on the chart very thin to be able to see the detail.
Open up the VBA editor by hitting ALT F11
Insert a new module by hitting Insert - Module
Paste the macro into the empty sheet
Hit ALT F11 to get back to the worksheet.
Run the macro by going to tools-macro in Excel 2003 or the view ribbon in Excel 2007/2010.