Net amount calculation for sales order

I have customized salesprice(unitprice) for an item but the net amount is getting calculated according to the item unit price.Can anyone help where to change the net amount calculation.

You may have to look upon following two methods for Net amount calculation

  1. SalesPurchLine Map → calcLineAmount method

  2. SalesLine table → modifiedField method

Thank you lalit and do you know where to change the line amount calculation only at the time invoice ??

Please can you tell me the exact situation what you want to achieve as i am not getting why anybody would change the line amount at the time of Invoice only.

The amount would change according to a newly added financial dimension-region.If suppose an item is having different prices in different regions and now i created a customer with region1 dimension on a particular day and im creating a sales order on another day , while invoicing i should be getting the least amount wrt the date of customer creation and sales order creation.