I have got two sheets with names platform and participant check

In platform (colomns), I had specified the details for the training
participants like
Name, Surname, date of training, venue, etc.... It could be above 700
participants

and in the participant check the 2nd sheet
when I type the Surname of participants it picks from the platform all the
details for the purticular participant.
the formula which I used is =VLOOKUP(B3,Platform!B:X,8,FALSE)
where as B3 is the Surname (which I have to type) PlatformB:X is the data
area and 8 is the 'first name' colomn on the platformsheet.

In the participant check I was hoping it to give me an option where once I
type the surname it shows me all first name if any with same surname. or on
another cell showing that there is another person with the same surname

Please help