Public Sub fnFieldAdd(strTableName As String, strFieldName As String, lngFieldType As Long, _
  Optional lngFieldSize As Long =  255 , Optional bFieldNullable As Boolean = True, _
  Optional bFieldZeroLength As Boolean = True, Optional bFieldUNICODEStrings As Boolean = False)
' strTableName - имя таблицы
' strFieldsName - имя поля в таблице
' lngFieldType -adVarWChar либо adLongVarWChar
' adoConn -существующее ADODB.Connection, наличие базы проверяется

    Dim bResult As Boolean
    Dim adoxCat 'As ADOX.Catalog
    Dim adoxTbl 'As ADOX.Table
    Dim adoxCol 'As ADOX.Column
    
    bResult = False

    Set adoxCat = CreateObject("ADOX.Catalog") 'New ADOX.Catalog
    
    adoxCat.ActiveConnection = adoConn
    
    For Each adoxTbl In adoxCat.Tables
        If adoxTbl.Type = "TABLE" Or adoxTbl.Type = "LINK" Then
            If adoxTbl.Name = strTableName Then
                For Each adoxCol In adoxTbl.Columns
                    If adoxCol.Name = strFieldName Then
                        bResult = True
                        Exit For
                    End If
                Next adoxCol
                If bResult = False Then 'если поля нет, то добавляем его
                    Set adoxCol = CreateObject("ADOX.Column") 'New ADOX.Column
                    With adoxCol
                        .ParentCatalog = adoxCat
                        .Name = strFieldName
                        .Type = lngFieldType  'тип поля
                        If lngFieldType = adVarWChar Then .DefinedSize = lngFieldSize
                        .Properties("Nullable") = bFieldNullable '
                        .Properties("Jet OLEDB:Allow Zero Length").Value = bFieldZeroLength ' разрешение пустых строк
                        .Properties("Jet OLEDB:Compressed UNICODE Strings").Value = bFieldUNICODEStrings 'Сжатие Юникод=Нет
                    End With
                    adoxTbl.Columns.Append adoxCol, lngFieldType
                End If
            End If
        End If
    Next adoxTbl
    
    Set adoxTbl = Nothing
    Set adoxCol = Nothing
End Sub

               For Each adoxCol In adoxTbl.Columns
                    If adoxCol.Name = strFieldName Then

Public Sub fnFieldToMemo(strTableName As String, strFieldName As String)
' strTableName - имя таблицы
' strFieldsName - имя поля в таблице
' adoConn -существующее ADODB.Connection, наличие базы проверяется

    Dim bResult As Boolean
    Dim adoxCat 'As ADOX.Catalog
    Dim adoxTbl 'As ADOX.Table
    Dim adoxCol 'As ADOX.Column
    
    bResult = False

    Set adoxCat = CreateObject("ADOX.Catalog") 'New ADOX.Catalog
    
    adoxCat.ActiveConnection = adoConn
    
    For Each adoxTbl In adoxCat.Tables
        If adoxTbl.Type = "TABLE" Or adoxTbl.Type = "LINK" Then
            If adoxTbl.Name = strTableName Then
                For Each adoxCol In adoxTbl.Columns
                    If adoxCol.Name = strFieldName Then
                        adoxCol.Type = adLongVarWChar
                        Exit For
                    End If
                Next adoxCol
            End If
        End If
    Next adoxTbl
    
    Set adoxTbl = Nothing
    Set adoxCol = Nothing
End Sub

Public Sub fnFieldDelete(strTableName As String, strFieldName As String)
' strTableName - имя таблицы
' strFieldsName - имя поля в таблице
' adoConn -существующее ADODB.Connection, наличие базы проверяется

    Dim adoxCat 'As ADOX.Catalog
    Dim adoxTbl 'As ADOX.Table
    
    On Error GoTo ToExit
    
    Set adoxCat = CreateObject("ADOX.Catalog") 'New ADOX.Catalog
    
    adoxCat.ActiveConnection = adoConn
    Set adoxTbl = adoxCat.Tables.Item(strTableName)
    adoxTbl.Columns.Delete strFieldName
    
ToExit:
    
    Set adoxCat = Nothing
    Set adoxTbl = Nothing
End Sub

Public Sub UpdateBD()
    fnFieldDelete "the_table", "old_name_1" 'string
    fnFieldDelete "the_table", "old_name_2"
    fnFieldDelete "the_table", "old_name_3" 'string
    fnFieldDelete "the_table", "old_name_4"
    fnFieldDelete "the_table", "old_name_5" 'string
    '---
    fnFieldAdd "the_table", "old_name_1", adLongVarWChar 'memo
    fnFieldAdd "the_table", "NEW_name_1", adLongVarWChar
    fnFieldAdd "the_table", "NEW_name_2", adLongVarWChar
    fnFieldAdd "the_table", "old_name_2", adVarWChar,  3 
    fnFieldAdd "the_table", "old_name_3", adLongVarWChar 'memo
    fnFieldAdd "the_table", "old_name_4", adVarWChar,  3 
    fnFieldAdd "the_table", "old_name_5", adLongVarWChar 'memo
    '=============================================
...    
End Sub