Gridlines - Different Scale
 

I have a chart, and the scale on the bottom is every week (mondays) and the
information is taken once a week. There wants to be verticle lines at the
begining of each month, but im at a loss how to do this.
I've tried going into the "Format Axis" on the chart and playing with the
scale, but it doesn't let me mix months and days.
Currently I have lines drawn on top of the graph with the drawing tools, but
I have to move these each time I do the report...