Best way is to find any standard FM which will fulfill your requirement.
My understanding for your requirement is below:
You are not finding unique entries in VBEP for the sales order items with more than schedule lines.
For example consider sales order 10001, item 10, qty 100. Lets say the order 10001, item 10 and qty 10 was delivered on a particular date, and the remaining qty on another date. This sales order, item will have two entries on vbep. This is one scenario.
So how are you planning to display this data? Display both the schedule line numbers for the sales order, item.?
Another scenario can be if the schedule lines are changed manually, there could be more than one entry.
So i would say one approach can be sort the VBEP internal table in descending order(So that latest entry would be on top) and pick the first entry, compare the ordered qty and delivered qty and display as per your requirement.(write logic If ordered and delivered quantities are not same. pick further entries from VBEP and compare).