Filtering Date Input

i am trying to build a marine turbine and parts log and have a problem in satisfying a working rule.

i have 2 tables which i have attached,

table 1 shows the on / off dates that a generator was fitted to a turbine

table 2 shows a general date history of the generator, when it had checks done, fitted, etc

what i would like to do is fit the generator again to another turbine

using a continous form to show the available dates in table 2, i would NOT like to see the dates during the period when the generator was fitted previously as shown in the on / off the dates in table 1.

the working rule being that a generator can not be fitted to 2 different turbines at the same time

can anybody point me in the right direction or assist in how i can overcome this problem

many thanks in advance for help provided