Automatic convert of initials to Full name

Hello everyone,
I hope you're all well. I have a simple Excel task I'd like help with through vba.

I want any initials I write in column A to automatically convert to the corresponding names in column D.

Importantly, the names populated in column A should not change, even if the content in columns C or D is deleted.

The list in columns C and D only goes up to row 100.

If the initials written in column A are not found in column C, I would like the cell in column A to display "not found."

Thank you for your assistance.