Dear Lilly,

Below is a step by step description of what Richard is talking about. Please adjust the code to suit your situation.
In the below example;
1. I have a Table named ProductT and four fields: ProductID (AutoNumber), CatalogNumber, ItemDescr and Result as Text fields. NB: WITH NO SPACES in the field names.
2. I have the sample data that you gave us as example in the table [WITH THE Result field left blank]
3. i create a form with a button and i have the code below in the On_Click Event
Dim db As Database
    Dim rs As Recordset
        
    Set db = CurrentDb
    Set rs = db.OpenRecordset("SELECT * FROM ProductT", dbOpenDynaset)
        
    While Not rs.EOF
        rs.Edit
        
        If InStr(rs!ItemDescr, rs!CatalogNumber) > 0 Then
            rs!Result = Replace(rs!ItemDescr, rs!CatalogNumber, "")
        End If
          
        rs.Update
            rs.MoveNext
    Wend
                    
    rs.Close
    db.Close
        
    Set rs = Nothing
    Set db = Nothing


Good luck in your project!

MICAH