You probably want to look at the optional MI module as it does exactly what you are after, graphs and all. You give it some KPIS to calucalte and it stashed them away daily and allows you to rport on them. The problem you might face otherwise is that crystal reports and queries give values at the point in time you run them. Re-run the report later and the values will be different. In general it's hard to look at an historical point in time with those tools. It's not impossible, but sometimes hard work and you have to change the design to dump the values you want. Or you run the query, export to excel, save and do the report from there
We are not licensed for the MI Module, so it would have to be a crystal report.
I do have a stored procedure that was created when the system was installed thats does something like what I am after but not quite.
I hope you can get it modified. You could alwways mail yourself the results of running the query/report every day and build up a picture that way.