The method below should cater for this, the sourceString can be either single characters or complete strings.
Public Function convertCharacters(ByVal sourceString As String) As String
Dim resultString As String = ""
resultString = sourceString.Replace(
"á", "a")
resultString = sourceString.Replace(
"é", "e")
resultString = sourceString.Replace(
"í", "i")
resultString = sourceString.Replace(
"ó", "o")
resultString = sourceString.Replace(
"ú", "u")
Return resultString
End Function
Hope this help!