Search and extract results to a txt file

Hi
I have an excel worksheet containing around 70thousand records. I am planning to write a macro that would search a string in a column (multiple occurances) and extract specific data from the row the string is found and output the same to a text file.

eg: Suppose column I contains the data i want to search for and suppose the search string is found at I3, I34, I130. Then I need to extract the following data in the following format in text file

A3,D3,I3
A34,D34,I34
A130,D130,I130

Appreciate your help.

regards
Vijay