language field in combination with global variable or fieldvalue

someone succeeded in using a global variable or a filed value in a lang_?

So suppose the lang_ is something like lang_test = ‘[usrname] is not allowed to delete this record’. When the message is shown the global [usrname] is changed by the user’s name. The same with a Lang with a {fieldname} in it. Possible to change by it s real value on the loaded form?