This is very much dependent on the platform provider and the funds you are using. It is important to appreciate that unlike share trading where you can make a dealing instruction that secures a (more or less) instantaneous market price, dealing with investment funds can take up to several days. In the best case scenario a switch instruction made before 10am will get the market price set at 12 noon on the same day. With some providers they will use the fund prices from the close of business on the following day.
Most funds are traded on a daily basis however there are some that are only traded once a week. So if a fund is traded (i.e. the fund price is set) on Wednesday and you make an instruction on Thursday it would be a further 6 days before the switch is made and in that time market conditions could change significantly.