EXCEL Macro - Find and replace function -Help

Hello, I work for a customer care ... I need to set a macro to delete customer information in the same file -- around 30,000 contact.

I was thinking to use the find and replace function - but it does ONLY work for the original contact ---

I can say find the text on C7 (customer address) then => check for the text in the file and replace the text to "UNK"

how can I define this code in visual basic.??????

Please Help