Excel 2008 : Formula to remove consecutive capital letters from text strings

With VBA a simple UDF should work:

Function CleanCapsAndNumbers(rngCheck As Range) As String
   Dim RegExp            As Object
   Dim strInput As String
   Dim strPattern As String
   Set RegExp = CreateObject("vbscript.regexp")
   strInput = rngCheck.Value
   strPattern = "([A-Z][A-Z]+|\d)"
   With RegExp
      .Global = True
      .Pattern = strPattern
      CleanCapsAndNumbers = Application.Trim(.Replace(strInput, ""))
   End With
End Function