Data entry to invoice - mobile

We are small builders who do jobs on a time and materials basis. We have 4 categories, Labour / Subcontractors / Plant Hire & Rubbish / Materials. Each week workers hand write timesheets, then this is transposed to Work Summary Books, then this is transposed to Excel spreadsheets (which look exactly the same) and these then tally up to be an invoice. Surely we can just fill in one timesheet (online?) then have it all roll into an invoice. The invoices are all in excel and they often lose formatting etc. This is simple workflow but it nees to be created to reflect our existing paperwork. [login to view URL] ------ 2. Work Summary of Job ------ 3. Invoice created (not in excel) -------- 4. Email invoice! Attached is a copy of what we use. How do you do it quicker and without errors. Is this possible to be made into a mobile app? Say on a tablet?