How to create a composite field with a dynamic value plus a static value ?

I created an Access Interface on which the user can maintain an Access SQL Server table. The table is comprised of fields
as follows:

                             BRANCH NUMBER           EMAIL ADDRESS PREFIX             EMAIL ADDRESS  
for ex:                   123                               JOHN.SMITH                              JOHN.SMITH@GOLDMAN.COM

Do you have a suggestion as to how I could ultimately have a user enter just a person's name before a
static value "@GOLDMAN value" into the field EMAIL ADDRESS PREFIX, which in the example above would be JOHN.SMITH and then I could have another field, named, for example, EMAIL ADDRESS which would contain the combination of the name the user entered (for ex: JOHN.SMITH) into the field EMAIL ADDRESS PREFIX plus the suffix @GOLDMAN.COM ?

My objective is to send emails to xxx@GOLDMAN.COM where xxx is the value in EMAIL ADDRESS PREFIX.
I did not want the user to have to enter the static value @GOLDMAN.COM at the end of each value for the field
EMAIL ADDRESS PREFIX. However, when I execute my Email address routine, I wanted to retrrieve the value as
xxx.@GOLDMAN.COM  

I realize that I could have my VBA email ACCEES routine concatenate the value @GOLMAN.COM to the end of each value for
EMAIL ADDRESS PREFIX but I was wondering if there is an alternative to save the value input by the user in 1 field named
EMAIL ADDRESS PREFIX and then have another field named EMAIL ADDRESS contain the EMAIL ADDRESS PREFIX plus the value "@GOLDMAN.COM".
I realize that this is not efficient but is there a way to do this ?