How to get the onAction input field value from table

Hi experts,

I have small problem in tables. I created one table with 2 fields.

1.Input Field.(Amount)

2. Text View Field.(Tax)

I will enter some amount in input field and i need to calculate tax and display in text view field. I created onAction() for input field.

Problem is:

1. Lead selection is always in first row, i am not able find the input field value for calculation.

2. How to find the input field value in onAction () method.

3. Any other setting i need to do ..

Regards,

Sunil