You can't do that with an Inputbox; Use a TextBox on a UserForm.
Option Explicit
'Allow multiple passwords
Const PWList As String = "Boffice, Foffice, GoOD1pA$$WOrd:
Dim PW As String
Dim Stars As String
Private Sub TextBox1_KeyDown(ByVal KeyCode As MSForms.ReturnInteger, ByVal Shift As Integer)
'You might need to experiment with Shift
'Save the Keystroke
PW = PW & ChrW(KeyCode)
Stars = Stars & "*"
End Sub
Private Sub TextBox1_KeyUp(ByVal KeyCode As MSForms.ReturnInteger, ByVal Shift As Integer)
'Display asterisks
TextBox1 = Stars
End Sub
Private Sub TextBox1_Exit(ByVal Cancel As MSForms.ReturnBoolean)
'Finished entering PW
Stars = ""
CheckPW
End Sub
Private Sub CheckPW()
If PW = vbNullString Then Exit Sub
If Instr(1, PWList, PW) Then
PW = ""
DoStuff
Else
MsgBox Prompt:="Incorrect password. Please try again.", Buttons:=vbOKOnly
PW = ""
End If
End Sub
Private Sub DoStuff()
'Fill in the blank
End Sub