Business Calendar and workflow

I want an online solution for my business. A Linux/php site that is password protected. Allows multiple users. User can insert data into a form, such as seen here: [login to view URL] This data will be inserted into a contract which will created and sent to me as a pdf file. The data will also be saved into a mysql database. The PDF file will be automatically uploaded to [login to view URL] into my account and sent to the appropriate person. When The file is signed, I need the site to then add this gig to a calendar by the click of a button. I also need to have the ability to add manually to the calendar. I want to be able to send emails to the people on the calendar by general rules (ie So many days before gig) or by specific rules for each gig.