Opening Different File Types With Ms Access 2003

hello good afternoon.
i am trying to open different file types using ms access. the following piece of code i found would only open 'word' documents. how do i make this piece of code more flexible to open pdf documents and excel as well. as it is currently i have a txt field on my form and if the path in the txt fiels leads to a word document when i click a button the word file opens. i want it to open a pdf or excel doc if it was in the txt field

[code]
Sub OpenWordDoc(strDocName As String)
Dim objApp As Object

'Opens the document

Set objApp = CreateObject("Word.Application")
objApp.Visible = True
objApp.Documents.Open strDocName

End Sub