passcode

answer = PASSCODE
creates a modal dialog box that returns user password input. Given characters are substituted with '*'-Signs like in usual Windows dialogs.

answer = PASSCODE
without input parameter allows to type any ASCII-Character
answer = PASSCODE('digit')
allows only digits as input characters [0-9]
answer = PASSCODE('letter')
allows only letters as input characters [a-z_A-Z]
answer = PASSCODE(<string>)
allows to use characters from the specified string only

See also PCODE.