Try this. Create a password form ("frmPassword"

with a single text box (I called it PasswordBox), an "enter" button, and a "cancel" button. In the form's module post the following code;
Function WhatisThePassword()
Dim Password As String
Dim Response As Integer
Dim strMsg As String
If IsNull(PasswordBox) Then
strMsg = "You must enter a password."
Response = MsgBox(strMsg, vbCritical + vbOKOnly, "Enter Password"
Exit Function
End If
If PasswordBox <> "Youguessedit" Then
strMsg = "You are not authorized to access this function."
Response = MsgBox(strMsg, vbCritical + vbOKOnly, "Incorrect Password"
Else
DoCmd.OpenForm "YourForm'sName"
DoCmd.Close acForm, Me.Name
End If
End Function
Private Sub cmdCancel_Click()
DoCmd.Close acForm, YourForm'sName
End Sub
Private Sub cmdButtontoOpenForm_Click() 'Calls the function
If IsitOpened = True Then
DoCmd.OpenForm "YourForm'sName"
Exit Sub
End If
DoCmd.OpenForm "frmPassword"
End Sub
'Determine if the Criteria Form is opened.
'If the form is opened, don't open the password box.
'Show the Form
Function IsitOpened() As Boolean
If IsLoaded("YourForm'sName"

Then
Cancel = True
IsitOpened = True
End If
End Function