How to set default screensaver on Mac 10.6 using xcode ?

Question

Hi all, I have created Following code to set my screen saver as default screen saver on MAC 10.6 (Snow Leopard). This code is working fine on our systems but when we distribute in installer then it does not set screen saver as default. Is it user permissions issue or some code problem ?the user login currently i am using is admin.

NSString    *path =  @"~/Library/Preferences/ByHost/com.apple.screensaver.";
OSStatus    err;
UInt32      numEnetEntries = kMaxEnetEntries;
char        enetstr[32];
EnetData    gedata[kMaxEnetEntries];

err = GetEthernetAddressInfo((EnetData*)&gedata, &numEnetEntries);

if(err == noErr && numEnetEntries > 0)
{
    MACAddress *eaddr = (MACAddress*)gedata[0].macAddress;
    EnetAddrToString(eaddr, enetstr);
    NSString *macAdd = [NSString stringWithCString:enetstr];

    macAdd = [[macAdd stringByReplacingOccurrencesOfString:@":" withString:@""] lowercaseString];
    path = [[path stringByAppendingFormat:@"%@.plist", macAdd] stringByStandardizingPath];
    NSMutableDictionary *plistDict = [[NSMutableDictionary alloc] initWithContentsOfFile:path];
    NSMutableDictionary *moduleDict = [plistDict objectForKey:@"moduleDict"];

        [moduleDict setValue:@"MyScreenSaver" forKey:@"moduleName"];
        [moduleDict setValue:@"/Library/Screen Savers/MyScreenSaver.saver" forKey:@"path"];



    NSNumber *yourNumber = [NSNumber numberWithInt:interval];
    [plistDict setValue:yourNumber forKey:@"idleTime"];
    [plistDict writeToFile:path atomically:YES];
}

Thanks