door chime, 02 cavalier

I have an 02 cavalier. I have an aftermarket headunit. With my vehicle you need to "relocate" the factory radio when installing an aftermarket headunit. So I ran the relocation harness back to my trunk and installed the headunit. With my car when I have my headlights turn on or open the door, I get the door chim from the driver side front speaker. All of my speakers though are ran off of amps and arent connected to the headunit at all (other than RCA's). Since this is so, when I turn off my car, but either have my headlights turned on or open the door, I dont get the door chime. What I want to do is hook something up so If I do leave my headlights on after I turn the car off  as soon as I open the driver side door, I want to have a door chime. I dont want to mess with the speaker, factory radio or anything like that. Instead I wanted to use a tweeter which I would mount under my dash and use some relays. Is there any way to achieve this? thank you in advance.

If you have installed the factory radio in the trunk and it powers up, all you have to do is use the left front speaker outputs from the radio to connect to a small speaker under the dash. Have the radio turned off in trunk and it will handle all the chime functions as required. Use a small speaker and not a tweeter as it won't handle the chime tones properly.sparky

Is there a way to use relay(s) instead? Somehow have them connected to the door trigger, headlight, and ignition wires instead of using the factory radio?  I mean I could use the relocation wire harness like you said. I could just find the front left speakers + and - wires and run them to a speaker under the dash like you had said. I forget what color that wire is, gray or white? And you said to use a speaker, not a tweeter. Well I cant put a 3 1/2" round under my dash. You are sure a tweeter wont work? I just need it to sound, not sound good.