measure and store current

Hi,
I need to measure and store in a SD a DC current flowing through a wire.
I thought to use a sd shield installed on seeduino mega. Sorry But my electronic knowledge is very poor and ask for your advice.
the second question is about software how can I do it?
Tks

FYI:
http://arduino.cc/en/Guide/Windows
http://garden.seeedstudio.com/index.php?title=GROVE_-_Starter_Bundle_V1.0b
http://garden.seeedstudio.com/index.php?title=SD_card_shield_for_Arduino