placeholder problem in asp.net(c#)?

[PranK]

i have 5 placeholders.one for principal,one for rate,one for months,one for interest,one for total amount and i am using 5 textboxes for 5 placeholders.i have 2 buttons,one calculate interest and other for total amount.now when i click the interest button everything looks gud.but when i click on the total amount the page gets empty.should i have to write the same program in total amount button.i dont want to calculate the total amount by using the formula TA=(P+(P*R*M)/100).i want that when i will click the interest button it will calculate the interest only and show it in the respective textbox.and when i will click on total amount button it will show total amount as well as all the information like principal,rate,months,interest.help me.plzzzzzzzzzz.