Randomize dut paramters in system verilog

I am writing a test bench in system verilog for a dut, and in the field it is possible for the parameter DEPTH to change and so I have been trying to figure out how to randomize a parameter. It is currently set at 20 but it has a range of 7 to 255. Any suggestions and help would be greatly appreciated.

I know you cant directly in the script randomize it but ive heard of others do it by creating a package that the run along side the test that can insert random values as parameters.