Exchange rate auto update on Sales orders

The client is processing and Saving sales orders and only opens and processes then a few days after capturing or the following week due to stock verification etc.

Upon re opening the Sales order the document retains the exchange rate of when the document was first captured. The client wants this rate to refresh and use the days rate when now processing the invoice.

Currently the rate must be changed manually to todays rate. Users sometimes forget to do this and process on an old rate.