Auto Complete field

I am using Access 2010 and I have a datasheet which records Invoice data:

Invoice number
Client ID
Client surname
Invoice date
Invoice amount
Date paid

Invoice number is the primary key and the table is linked to the Client
datasheet.

I would like to be able to enter the Client ID in the Invoice Datasheet and
have Access auto complete the Client surname field. Is that possible? Would
I need to build an expression or is there something in Design that can be
used?

All help appreciated.


Steve