Do an equal comparison (==) between RC_flag and zero, generate this int_flag. Feed int_flag to an Integrator. If the output of the Integrator is greater than 5, then execute the subsystem.
Enable the external reset of the Integrator block. Use the int_flag and specify "falling" edge to reset the Integrator. Any change of the int_flag during the 5 seconds will reset the Integrator block.