Yah - what does the data in the secondary table look like? Just date values? Are you looking for an exact match - user selects 2016-11-15 and you want back just the last three digits from another field in a row that has 2016-11-15? At any rate, I created a simple sample - save the attached file locally, right click and select Design, then you can preview. If the data is a fixed length, you should just be able to use a substring formula. If it varies, the formula will be slightly more complex. If the date is an exact match, you can just use a filter to get the right row - if it is a range, that gets more complex (again) - but hopefully this will help?