How to create a public variable in a private module

Question

Basically It's a login form and i'm trying to save the ID which is the Me.CBOUsername.Column(0) but I get an error when i try to call it in another form.

Option Compare Database
Option Explicit
Public ID_ As String
Private Sub Command4_Click()
    Dim strCBOPass As String
    Dim strPassword As String

    strCBOPass = Me.CBOUsername.Column(1)
    strPassword = Me.txtpassword

    If strCBOPass = strPassword Then
        MsgBox "Login Successful!"
        DoCmd.OpenForm "Form1"
        DoCmd.Close acForm, Me.Name
        ID_ = Me.CBOUsername.Column(0)

    Else
        MsgBox "login Unsuccessful!"
    End If
End Sub

Answer 1

It may be a little easier to explain this way.

As an example of a global variable:

Public Global_Variable1 as String

Public Sub Procedure1()
    Global_Variable1 = "Test"
End Sub

Public Sub Procedure2()
    Call Procedure1
    MsgBox (Global_Variable1)  'return Test
End Sub

Add the module by right-clicking, and using Insert > Module