need to reduce the value for runtime in gridview in asp.net
i have bind the value as billamount in grid and i have the textbox and i enter the value in runtime i need the output in the grid.
| Name | Date | billamount | |
| Celv | 14/4/15 | 15000 | |
| celv | 25/4/15 | 25000 | |
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Now In runtime am giving amount as 20000 .
| Name | Date | Billamount | | |
| Celv | 14/4/15 | 15000 | 20000 | 5000 |
| Celv | 25/4/15 | 25000 | 5000 | 20000 |
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I need to reduce the amount 5000 for the next date in asp.net