you can set values to the dataset using ado.net features.
when you get data from sql
use datatable object and change the values as per you need like below
for(int i = 0;i<dt.roww.count;i++)
{
if(discount != 0)
{
double newvlaue = oldvalue + (oldvalue * discount)/100;
datatable.rows[0]["price"] = newvlaue
}
else
{
keep price as it is
}
datatable.acectpchanges();
repeater.datasource = datatable;
repeater.databind();
}