Adding a calculated formula-text field with the above formula will translate all selections in that address state field in any new or existing record. When you report on the record, you can then utilize the new formula text field in the report instead of using the field that spells out the state.
Let's assume that your current field that spells out the state names is called "State". Add a formula-text field called "State Abbreviation". In the field properties of that new field, copy and paste for formula above, like this:
Case([State],
"Alabama", "AL",
"Alaska", "AK",
"Arizona", "AZ",
"Arkansas", "AR",.....
This will give you a new field, and since it is a formula field, it will work for both new and existing records (assuming that a state is selected). When you need to report on an address, simply pull the new "State Abbreviation" field in your report.
