Web based timesheet system

Hello, i would like to add web based time sheet system for my website.
Idea is that employees for my agency would register on the website and so does the clients. Then employees would fill their time sheets online and at the end of the week they would send it to me i would then recheck it and forward it to clients profile page on my web for them to confirm and it would automatically generate invoice for me to recheck and edit if needed and then i could send it to clients page again. Hope you get the idea. This all should be that difficult but im still beginner at php and databases and html. But for now is there a way to modify a plugin or maybe there is a plugin that could be easy converted. I am thinking of Contact form 7 if it could be assigned for a users profile then there might be a way to make it for for my idea.
All help would be much appreciated.