Identifying ADC pins using "Symbol"

The following code does not work. Obviously I am doing something wrong.
Code:
Symbol Speed= AD0
..........
...........
Readadc10 Speed,W4
I know that it will work if I use:

Readadc10 0,W4

But is there a way to identify an ADC pin using Symbol?
I am using a 28X.
 
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