Trouble with MikroC and motor controls

Hi. I've got a RoboPica v2.0 robot kit and I'm having trouble trying to get motor functions to work. It seems to be a problem with the Pwm1_Change_Duty() command which I'm told to use in the manual. MikroC PRO for PIC doesn't seem to like this command and gives an error message when I try to build a hex file. But when I use Pwm1_Set_Duty(), which it accepts, and upload the hex file to the robot, it doesn't work properly. The piezo rings and the M-1 and M-2 LEDS remain red while one of the motors has small 'spasms'. The code I used to test this is PWMTest01.c on the CD under A4-1.

Any help would be greatly appreciated
Cheers