open price, back testing and the reality

[waheeb <WAHEEB@xxxxxxxxxxxxxx>]

I am back-testing a system in which all the trades will be executed next
day at open price.
Say xyz opened last Monday (historical data) at $15.75 and my question is
this valid to back-test.
I always see bid & ask range regard less of the time (at open or at close).
Any comment on this.
 Also does anyone know how to forecast the next day opening price.

Thanks

waheeb