how to create cronjob trigger except few minutes in every hour

Hi,

I need to create a cronjob trigger to run every 15 minutes. But i would like to exclude the cronjob not to run between 11 AM - 11.29 AM & 9 PM - 9.29 PM.

INSERT_UPDATE Trigger;cronjob(code)[unique=true];cronExpression #% afterEach: impex.getLastImportedItem().setActivationTime(new Date()); ;myJobName; 0 0/15 * ?

I know that this will run for every 15 minutes. But how do i specify the exclusions? Please help.

Thanks Vidhya