InfoPath Dev

hello anybody. in info path 2010 i have a drop down list that show several time to user for select a data. and i have a repeating table from this form that show last times that users selected it until user know that it time is reserved. i want, when new user try to select new time from drop down list . if it time, there is in repeating table, show error to user that it is reserved. on drop down list write rule to check it but As though the rule check first item in repeating table. how to check new item with all repeating table list items. thank you so much.

no every body to help me

When you select the field from the repeating table for comparison, you should see a drop down - you can select "Any instance of" for the field - that should create an expression that checks all instances.