Relationship between databases

Relationship between databases

I have a database with details of all my clients (about 20 in total)

I have another form which my clients use to book an appointment and I need to know who is making the booking.  I want the client name entered on the booking form to equal the client name in the client list and I do not want the client to use a drop down box as I do not want clients to know who my other clients are ...

Is there a way for creator to ensure fields match without disclosing the options