Aggregate data values before 30 minutes and after 30 minutes of specific time

Hello All,

I am seeking help with a time dimension. My intention here to aggregate values which are happening 30 minutes before and after each and every time interval. For an instance at 630 (see attached worksheet) I want to add all such values whose negotiated time (NEGTIME) was 600 hrs and 700 hrs within the 630-time interval and same with 700 hrs time interval (Like occurrences whose negotiated time is 630 hrs and 730 hrs). Please advise. Let me know if you have any questions. Thanks