Code:
It is not standard.
There are certain loose guidelines, but it does vary from person to person and/or course to course.
This may or may not fit in with your design but here goes.
Create a Table. Call it tblSalary.
PK "AutoNumber"
Description "Text"
Wage "Currency"
Enter some data in Table DataSheet view. This Table does not need to be Related to any other Table/s
In your form where you enter the Salary, Bind a Combo Box to a Field where you are going to store the Salary. "Currency" This is not a Foregin Key as you will be storing the actual Salary in $0,000.00 Format.
Link the Combo Box to the new Table tblSarary so that you can pick from the list. In the Properties of the Combo Box DO NOT LIMIT TO LIST.
This way you can either select a preexisting Value or Free Type a new one. The Result will be stored in the Record Source (Table) behind the Form.
This is not normal practice but may be a good option for you as not All Salaries are Standard.