Quote:
I was wondering if there is a way to generate a one time only passcode to enable a software download from a fileaharing website, for a software that I will be posting?
"a one time only passcode to enable a software download" is the wrong place to put protection.
A better choice is to use a license activation scheme. After installation, you software ask a purchase code and register on your site so that the purchase code can not be reused for another install.