To set the whole document to Spanish (or any other language), create the following macro:
Sub SetSpanish()
'
' SetSpanish Macro
'
'
pos = Selection.End
Selection.WholeStory
Selection.LanguageID = wdSpanishModernSort
Selection.NoProofing = False
Application.CheckLanguage = True
ActiveDocument.Save
Selection.Start = pos
Selection.End = pos
End Sub