Advanced PHP and MySQL Form for Joomla (breezing / facile forms intergration)

Hi
I urgently (within next two days!) need someone to implement a form on a 1.5 Joomla instance using breezing forms. All the fields and unique names have been set up in the front end ready. The front end needs a cloneTrue script so the user can add extra rooms and this is done with CSS already have this already. The bit I can't do is how to implement a simple calculation resulting in a value shown in the backend field which is the "heat requirement" (a hidden field?). The formula for calculating the "heat requirement" is Heat Requirement = Room Vol x Heat Loss Factor x Temperature Difference all divided by 2800.

Notes:
1. Temperature Differences:
Lounge, Dining Room, Study, Kitchen, Hallway & Conservatory would generate a Temp. Differerence of 27.5Â’ºC in Location 1, 30Â’ºC in Location 2 and 32.5Â’ºC in Location 3

Other rooms would be 2.5Â’ºC less per location

2. Heat Loss Factors HLF ( based on sheltered location)
Insulation Standard:
Poor= HLF 5 except for conservatory, which would have 6
Average= HLF 4.5
Good = HLF 4
If Location exposed then 0.5 to be added to HLFs.

If the project is done within 24 hrs a bonus of £50 will be paid ontop of fee. Any questions get in touch.