With dial-up & 1 phone line, can you forward your calls to a cell phone?

[hopein08]

It was a while ago, so I'm sketchy on the details, but I remember my uncle telling me that I can use put my land line number (i.e. only phone line) into my cell phone with two numbers in front (72 or 27, perhaps?) and then, while I'm online...I will still get the calls coming in to my land line, only on my cell phone. Does anybody know if this is true?