add another Property like initial Value from Siblings Fields or a Formula

[Aneeskhan]

How to add more customize property like initial value from another field or calculate initial value from the value of another fields value based on formula and if valve is changed in siblings fields Initial Value should re-calculated on blur or onchange. how to achieve this functionality ? i have attached an image too.

[sudhamsh-kodam]

How to add properties or custom properties if any one can explain with example that would be really a great help.. hoping some one to come up