So you just wanna chart any interface that hit 90% utilization correct? How many interfaces are we talking about? Depending on the number of interfaces that could be reporting a 90% utilization, this may not be legible in the chart at all. You may be better of reporting on a table. Getting your timestamped utilization per interface.
Creating custom charts using custom SQL queries are straight forward. I would often get a request to chart out utilization on circuit on a previous week during business hours only. These are normally limited to a handful of circuits. It can be done but you may need to be able to do them in smaller groups.