HI< I NEED SOME REAL HELP!

I have downloaded Limewire, and done some downloading, but i need to set a time for my downloads, for example if i want all the things i want to download at 1am in the morning, then how do i make it so, ??? plz help me
Im doing this because i have limited internet, and hav peek and off-peak limits, HOW DO I SET A TIME< SO ALL MY DOWNLOADING HAPPENS AT ONE SPECIFIC TIME I SET????