Recording Cell Phone Calls

Right now I own a handheld digital voice recorder, but I may need to be able to record a cell phone conversation soon, since I need to do an interview that may end up being over the phone, and my only phone is the cell . . .

Is there any way to connect the cell phone to the digital recorder so that I can record the conversation using that? Or is there something inexpensive that I can buy that will allow me to record? I know there are things you can buy to record conversations on a regular land line . . . but Im not sure with the cell phone.

Its pretty important. Any help is really appreciated!