If you don't want to add a complete module, you can add just the missing procedures to an existing module by using the macro below. It adds the content of a text file to an existing module:

Sub ImportModuleCode(ByVal wb As Workbook, ByVal ModuleName As String, ByVal ImportFromFile As String)
' requires a reference to the Microsoft Visual Basic Extensibility library
' imports code to ModuleName in wb from a textfile named ImportFromFile
Dim VBCM As CodeModule
    If Dir(ImportFromFile) = "" Then Exit Sub
    On Error Resume Next
    Set VBCM = wb.VBProject.VBComponents(ModuleName).CodeModule
    If Not VBCM Is Nothing Then
        VBCM.AddFromFile ImportFromFile
        Set VBCM = Nothing
    End If
    On Error GoTo 0
End Sub

ImportModuleCode ActiveWorkbook, "TestModule", "C:\FolderName\NewCode.txt"