Calculation based on checkbox and another field

Hi all,

I need your help with javascript for calculation of value based on checkbox and another field. Based on field (area) and three checkbox another value should be calculated.

1. Field Area - house area

2. Checkbox 1 - 8% tax

3. Checkbox 2 - 23% tax

4. Checkox 3 - 8/23% tax based on house area. For the area of the house greter than 300 tax is mixed. For example: area of the house is 350, 8% tax is calculated to 300 and 23% for 50.

5. Field Price

6. Field Gross Price

Fields Area and Price are filled by user. Checkbox 1 is selected by user.

Calculations:

Filed Gross Price =

If Checkbox 1 is selected: Price * 1,08

If Checkbox 2 is selected: Price * 1,23

If Checbkox 3 is selected, Area field is eg. 350. Tax is divaded to 300 and 50 (Area-300): Price + (Price/Area * 300 * 0,08) + (Price/Area * (Area-300) * 0,23)

Thank you for help!