Calculating Max of Sub-records for Main Record

[jh51745]

I have a table with main records and another related table that are Sub-Records of the main. The sub-records are tasks with start and finish dates for each task. I would like to find the total time to complete the main record by getting the earliest start date and latest finish date for each task and the calculating the difference. what would be the easiest way to do this? I can't find a way to do it via calculated field.

[Perceptus]

If this is all contained within a form and subform, i would add a header/footer to the subform with a textbox with dsum, then reference it on the parent form. do you have an example db?

Use your calculated logic in a dsum statement. not sure how that will work on performance.