Hello,

I have two sheets named as "Atmos" and "Surface" in a single Excel file . What I'd like to do is to copy the data in "Surface Condition" and "Surface Temperature" columns in "Surface" sheet and paste them into the columns in "Atmos" only when their "Station_Name" AND "Observation Time" match, and write "N/A" when there is no matching record. The actual dataset contains nearly 0.5 million rows to match and copy from.. I've tried Index & Match and it worked for a fairly small file but was taking way too long for my actual dataset. Please help me to write an efficient VBA script for this...... Thanks!Click image for larger version. 

Name:	Atmos.JPG 
Views:	10 
Size:	94.8 KB 
ID:	2877Click image for larger version. 

Name:	surface.JPG 
Views:	5 
Size:	54.7 KB 
ID:	2878Sample.xlsx