Not possible to add Zero at the left side within excel cell

Hi,
I have got 500 faxing contacts listing from ms excel to outlook 2007. Fax broadcasting is our plan to implement through “win fax pro 10.02”. The fact is 0 can not be attached at the left side within excel cell. For automatic running of fax broadcast we have to add 0 then will have to dial the following numbers. How could it be solved without dialing every time manually?
Thank you for your assistance
