3818066 - How to create an expense type with a default (constant) amount?

I want to create a default amount expense type, for example a US Visa fee which I know as always 190 USD. It's necessary to avoid any user  change in the defined amount. How can I do that?

I want to create a default amount expense type, is it possible? , KBA , CON-CA-ADM-PAS , Policy Assistance , CON-EXP-ADM-EXT , Expense Types , CON-EXP-ADM-AUR , Audit Rules , CON-EXP-ADM-WFL-WL , Workflow , CON-CA-USP-CRC , Credit Cards , Problem