PHP form bug fix and mod

I am once again in dire need of expert PHP / MySQL coder to fix some bugs in an existing PHP form. It is basically an online registeration form that based on options that user chooses, it adds the total amount and ties in with [login to view URL] for payment processing. Bugs to be fixed: -Some of the calculations are wrong. -Would need a randomly generated confirmation number attached to each form submission. -Date and time of submission added to database - an extra comment field be added in the admin panel - currently the form has a "total" box that keeps track of total of items purchased. Unfortunately this amount can be modified by users. It must not be modified by users. - fields could be added to the form via admin panel. Bug exists where new fields are not counted in the total box. eg: if I add an extra item that could be purchased, the price of this new item does not get added to the total price. Due to the urgency of this issue, I have no choice but to list this project rather than working with my trusted providers who are currently busy with other projects. However preference will be given to providers I have worked with previously. Thanks.