How to set NStextfield displayed as **** return character when checkbox in cocoa

How to set NStextfield displayed as **** return character when checkbox in
cocoa

I'm a newbiwe. I building a mac app, i want to set type input in password
textfield displayed as **. And then user check on Checkbox, text in
password textfield displayed normal. I created NStextfield and Checkbox
programmitically. Thanks for your help.