INP commands

Hello,

I am Very new To Qbasic yet have the need to work with the INP command..

Using the parallel port i will be connecting a cable with differing voltages. All I need is for the program to determine the input voltage and then do different things....

for instance if the input voltage is 4 volts then.....
if same input = 5 volts then do something else...

This may be a simple question but help will be appreciated.