@emmajayne Perhaps the attached file can give some inspiration. The first graph is a stacked bar chart, where the first series holds the "real" measurement and a second series with small values that act as markers. Set the format of the first series to "no fill" and you are left with a small square directly outside the "real" measurement.
Easier would be to allow the names to be on the horizontal axis. Choose a line chart with markers and "no line" as the line format.