You can mess about with what is displayed, but its quite simple.
Hope this helps - code below
Code:
Dim stDocName As String
Dim stLinkCriteria As String
Dim PassWordtxt
PassWordtxt = InputBox("Please Type in password")
If PassWordtxt = "password" Then
stDocName = "NAME_OF_FORM_TO_OPEN"
DoCmd.OpenForm stDocName, , , stLinkCriteria
Else
MsgBox "The password provided was incorrect - you do not have permission"
End If