Help creating a barcode textfield value

guys, i need help with creating/converting a text value into a barcode readable format. i already have the barcode font but i don’t know how to put asterisk(*) into the dynamically obtained text value. The asterisk is a qualifier, barcode scanners need this to let them know where to start reading and to end. thanks.

example: 12345. i need to convert this into #12345.