using check box in modulepool program

HII gurus

i have requirement that I taken two check boxs one is 'SAP' second one is 'ABAP'

when i select ABAP it should print abap in text field same with SAP

when i press both check boxs SAP And ABAP i should get 'SAPABAP' in TEXT field when i press ABAP AND SAP i should get 'ABAPSAP'

please send the logic required

thanku

regards

sudheer