And maybe add the exchange rate, so that you don't have to calculate it manually.
By exchange rate, what do you mean? If you mean pulling from BTC-E or similar, this could be done but would have to be a future addition. If you mean the fee, this should be shown to you during the create a new trade screen.
If the trade is e.g 75WDC for 1.5LTC you could display the rate for 1LTC or 100WDC (which is typical for these kinds of trades). That way the buyer does not need to check manually if the rate is correct.