How to add extra axis labels in a logarithmic chart in Excel 2010?

I need to add some additional vertical axis labels to a logarithmic chart in Excel 2010.
You only get 1, 10, 100, 1000, etc. as standard.

My data goes from 100 to 4000 and i would like to add 200, 500, and 2000 as additional axis labels.

I apologize if the solution to this has been posted.
I looked for it but could not find anything.