Lookup wizard

I don´t know if there is a solution. But maybe somebody have an idea

I mad a reservation table with the fields Data, Time, Airplane, Instructor. Now i will add a new reservation with Data and time. on the Airplane field i use the lookup wizard and chooce the table with the airplanes. but now i would like that the drop down field airplane just show those aiplanes which not have a reservation already on the same data and time.For this i need to make a where statment with a database select command in the lookup wizard for the airplane field.

I use the PHPrunner

Any help please? Thank you in advance