MS Access Form Browse Button

I have been utilizing the attached code to allow users to browse for a file within a directory and insert the filepath into a field. It worked great a few days ago, but all of a sudden it is giving an error: 'Compile Error: Sub or Function not Defined'

It highlights ahtAddFilterItem. I do not understand why it is doing this since it worked fine a few days ago. I cannot think of anything that changed.

Why am I getting this error?

Note: I did not generate this code, I found it here: https://www.experts-exchange.com/questions/21554625/Adding-a-browse-button-in-MS-Access-2000.html?sfQueryTermInfo=1+access+brows+button+form+ms

Private Sub BrowseTREND_Click()
 
    Dim strStartDir As String
    Dim strFilter As String
    Dim lngFlags As Long
    
' Lets start the file browse from our current directory
     
    strStartDir = CurrentDb.Name
    strStartDir = Left(strStartDir, Len(strStartDir) - Len(Dir(strStartDir)))
 
    strFilter = ahtAddFilterItem(strFilter, _
                        "Word Documents (*.doc)", "*.doc")
 
    strFilter = ahtAddFilterItem(strFilter, _
                        "Excel Files (*.xls)", "*.xls")
    strFilter = ahtAddFilterItem(strFilter, _
                        "All files (*.*)", "*.*")
 
    Me.FilePath = ahtCommonFileOpenSave(InitialDir:=strStartDir, _
                     Filter:=strFilter, FilterIndex:=3, Flags:=lngFlags, _
                     DialogTitle:="Select File")
End Sub

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