Word 2010 Compile error: "Sub or Function not defined"

Hello from Steved

12:27 PM  RACE 1 - 18 Jan 2014  PUKE  Fine  Good  3.0  R85  $17500  2200  Ch : 1 

Why am I getting the below error please.

Compile error: Sub or Function not defined

blnRet = CheckItemExists(arrRightText, strItem)

Sub DemoCheck()
     Dim arrRightText
     Dim strItem As String
     Dim blnRet As Boolean
    
     arrRightText = Array("ELLE", "HOKI", "PAER", "PUKE", "RAUK", "TAUR", "TEAW", "TETE", "THAM")
    
     strItem = InputBox("Please input a word: ", "DlgBox")
    
     If StrPtr(strItem) = 0 Then
         Exit Sub
     Else
         If Trim$(strItem) <> "" Then
             blnRet = CheckItemExists(arrRightText, strItem)
            
             If blnRet Then
                 Application.ScreenUpdating = False
                 DoReplacing strItem, arrRightText
                 Application.ScreenUpdating = True
             End If
         End If
     End If
 End Sub