Show look up results in user form and display warning if overwritting existing entry

Hi GuRUss,

I have an excel worksheet for entering invoice data. (pls look at the attachment)
I would like to add another function on the same userform so that it could display historical data as well. Whenever i happened to overwrite the old data, a warning message will be prompted.

Any ideas on the aforementioned problem?

Please help.

YJL