adc conversion using PIC 16f877a

hi,

can we assign any conversion channel to perform a conversion..
example: i have 2 ultrasonics range sensors and i am measuring the distance to a wall.

from tutorials, it say the first conversion can be done in channel 2. i.e.

distance_1=Adc_Read(2);

now i want to measure the distance using the second sensor..

distance_2=Adc_Read(?);

which channel do i use here??
am using mikroC..

its urgent guys.. please help..

cheerz,
satanas