The market has swung about 1% today (GBPEUR from high to low) Euro and we have seen inexcess of this movment most day this week. These type of conditions are ideal for clients who need to move funds in the short terms and have a target rate in mind. You can place a limit order so that if a particular price is possible you currency will automatically be purchased.
The level you set your order at can be discussed with your broker as you need to set a realistic level if you want it to fill in the short term (for longer term orders your strategy may be slightly different). So with a short term limit order once you decide an appropriate level, you then place the order and if that price is possible at any time of the day, any day of the week your funds will be purchased for you.
Once a deal is done you then send your funds to complete the contact. I have had a great deal of success for my clients today as the market spiked and then dipped allowing clients buying to benefit this morning and clients selling to fill their oprders this afternoon. A good day all round!