Since VB6 is ancient and I don't have it up and running I'll share how I do this in just about every coding system.
- Add the usual ONCHANGE event responder.
- In the onchange event responder, change to the selected item as you wish.
Maybe you are asking for me to code this for you but last year we ended the last VB6 support at the office and wiped the machines that had it. We're not looking back since there is no revenue there.
If you forgot how to set the list index, read https://www.vbforums.com/showthread.php?259445-Set-combobox-listindex-with-known-ItemData-RESOLVED