CVI ships with a function panel that includes functions for a password control (...\cvi\tollslib\custctrl\pwctrl.fp) and a sample project that shows how to use it (...\cvi\samplesuserint\custctrl\password\pwsample.prj).
You need to add pwctrl.fp to your project, then you can create a password control in one of two ways.
1. You can create a password control in your code using PasswordCtrl_Create(), specifying the position of the control on the panel.
2. You can use the UI editor to place a string control on your panel and then use PasswordCtrl_ConvertFromString() to use that control to enter a password and mask the characters as they're typed.
I like PasswordCtrl_ConvertFromString() because it makes it easier to design your panel graphically.