You can only reference the value of a field.
Are your values and the display name the same? I will assume they are different.
One option is to bind your dropdown to a seperate field where you can keep the value for your use and set the value of the original and other fields as needed or create an input table which has the display name and values which can be a secondary data source so you can resolve the value and the display name anywhere in your form as well as use it for your drop downs.
I would recommend a simple XML list that will have this data table which can be used as a data source in your form.