InfoPath Dev

I am creating an infopath form and I have a choice field of different start times for a user to choose from. I want that chosen time to appear disabled if it has been chosen. I can't get the rue to work. Do you know how I can accomplish this? Example: 7:00 AM if 7:00 is chosen I want it to be unavailable (read only) to the next user 8:00 AM 9:00 AM Your assistance is greatly appreciated.

How will you know if someone else has selected the time? Does the form submit to a SharePoint Library, for example? If so - you could promote the "time" field and then query that library in order to know if it should be selectable. I don't know if you'll be able to make it appear disabled, but you may be able to prevent selection in other ways - I'd need to see your form in order to have a better guess. :)

The form does submit to a sharepoint list. My "Start Time" column is a field within the list. I also created a separate list because i started with a lookup field in sharepoint. I wasn't successful with trying each way. So within the list my "Start Time" column can i make this condition work. Could the query work this way? my list a text field of times ex: 7:00, 8:00, 9:00 etc. If a user selects 7:00 i want that time to be reserved for the next user. so the user would choose a date from the "Date" column (2 dates) but i only have one list because the times are the same. i have files attached.