Go here for example code and it may also answer your question.
http://www.rentron.com/PicBasic1.htm
Then scroll to:
A/D & Using The 8-Pin PIC™ Series
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Click HERE for: How to build a 4-channel A/D converter using the PIC12C671.
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Click HERE for: Using the 8-Pin PIC12C671 A/D Converter.
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Click HERE for: Using the 8-Pin PIC12C671 with PicBasic.
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Click HERE for: Using the PIC16F877 A/D Converter. This example displays 3-channels of analog input on an LCD display.
Never had any problems with more than one myself.