Dear Sy,
Jonathan's suggestion is a good one. Once you express the SREC in $/kWh, you can use the PBI option on the Incentives page to model the SCREC. You can use the Annual Schedule option to specify an SREC for each year.
For example, one value for Years 1 through 5, and a second value for years 6 through 10, etc. Here's a screenshot to help you see what we are describing:
Best regards,
Paul.