i end up doing this

unsigned char Ow_Reset(ibutton_io)
{
switch (ibutton_io)
{
case 0: Reader_I = LOW; // pull 1_Wire line low
us_Delay(29); // leave it low for 480us
Reader_I = HIGH; // allow line to return high
us_Delay(3); // wait for presence
if(Reader_I) // if line is high
return 0; // no part presence
else
{ // get presence signal
while(!Reader_I); // wait for end of timeslot
return 1; // 1=presence, 0 = no part
}
break;

case 1: Reader_A = LOW; // pull 1_Wire line low
us_Delay(29); // leave it low for 480us
Reader_A = HIGH; // allow line to return high
us_Delay(3); // wait for presence
if(Reader_A) // if line is high
return 0; // no part presence
else
{ // get presence signal
while(!Reader_A); // wait for end of timeslot
return 1; // 1=presence, 0 = no part
}
break;

case 2: Reader_B = LOW; // pull 1_Wire line low
us_Delay(29); // leave it low for 480us
Reader_B = HIGH; // allow line to return high
us_Delay(3); // wait for presence
if(Reader_B) // if line is high
return 0; // no part presence
else
{ // get presence signal
while(!Reader_B); // wait for end of timeslot
return 1; // 1=presence, 0 = no part
}
break;
}


}

Not classy - But it works