Take a look at the following from the Access Help file it might be what
you're looking for...
Extract a part of a text value
The following table lists examples of expressions that return a part of a
string.
You can use these expressions in calculated controls (calculated control: A
control that is used on a form, report, or data access page to display the
result of an expression. The result is recalculated each time there is a
change in any of the values on which the expression is based.) on forms,
reports, and data access pages (data access page: A Web page, published from
Access, that has a connection to a database. In a data access page, you can
view, add to, edit, and manipulate the data stored in the database. A page
can also include data from other sources, such as Excel.).
Expression Description
=Left([ProductName], 1) Displays the first character of the value of the
ProductName field.
=Right([AssetCode], 2) Displays the last 2 characters of the value of the
AssetCode field.
=Mid([MyString], 18, 4) Displays "Emma," if MyString contains the value
"Congratulations, Emma."
You can use these expressions in a calculated field in a query.
Expression Description
ProductInitial: Left([ProductName], 1) Displays in the ProductInitial field
the first character of the value in the ProductName field.
TypeCode: Right([AssetCode], 2) Displays in the TypeCode field the last two
characters of the value in the AssetCode field.
AreaCode: Mid([Phone], 2, 3) Displays in the AreaCode field the three
characters starting with the second character of the value in the Phone
field.