Excel 2007 :: Inconsistent Time Scale - X Axis

Basically I have some performance figures for a fund that I want to make a chart for, the problem is that the first date (the start date of the fund) is 15/09/2011 but every reporting date after that is the end of the month.

So my data looks something like this (not real figures)

15/09/11 20
30/09/11 22
31/10/11 23
30/11/11 25
31/12/11 26
31/01/12 27.5
29/02/12 29

So what I want is a graph where the x axis starts at 15/09/11 but then the next label is 30/09/11 and 31/10/11 etc, while still keeping the scale proportionate to the dates, ie the distance between 15/09/11 and 30/09/11 will be half the distance between 30/09/11 and 31/10/11.

The 2 outcomes I seem to be stuck with is either forcing the graph to start at 31/08/11 and making the y axis cross at 15/09/11, however with this the x axis goes left past the y axis cross point and it just looks dumb, although everything right of the y axis is correct.

Or secondly I get the graph to start at 15/09/11 and set it to label every 1 month and all the labels are 15/09/11, 15/10/11, 15/11/11 etc

I have access to excel 2003 or 2007.