Textbox Update Problem

I have a textbox on a form in which a customername will be displayed after a combobox with customercodes is updated.

Now, I have both a change and on enter event, which should save the customername into a table.

This works fine, as long as I only have one entry in the table.

As soon as I enter a second entry, it somehow deletes the customername for the previously entry.

If this is not clear enough, maybe this will help:

table:

customercode | customername
12345 | customer a

after entering the second customercode, I get this:

customercode | customername
12346 | customer b
12345 |

so it displays only one customername a time.

Is there any way to solve this?

Thx,

Lion85heart