home networking 2 computers on one line

i have 2 computers setup at home on a ehternet and i want both to be able to connect to the internet. I have 1 phone line and have to share the line between both computers! so if i have computer 1 dial up i can get computer 2 to connect threw internet connection sharing now i also want to do it the other way round so that if computer 2 has used the phone line and dialed up to the internet then i want computer 1 to connect threw internet connection sharing threw computer 2 please help thanks