Looking for a Plugin, which allows me to assign users to forms

Hi,

I’d like to send out lists / forms to my clients to let the medit the forms. Right now I’m sending out excel spreadsheets and await their reply with a filled excel spreadsheet.

Unfortunately my clients always change the format of the spreadsheet and when they want to update, I need to replace existing spreadsheets, etc.

So, I’m looking for a mechnism, which lets me send out the form to a client. The client needs to create a user on my site to edit THEIR form(s). The client will be able to update the form and to create new forms or I assign them forms to their user.

Is there a suggestion for a plugin or any other idea?

thanks a lot!