1 sheet contains data with details to whom we want to give letters. We have a letter format in Report sheet, and we want to apply mail merge through VBA in which we want to change the letter details as well. Let’s understand with a simple exercise:. To perform such operation, we use Microsoft Word. Mail Merge: - This is the source to merge the data’s information into text and then print the document. In this article, we are going to learn how to automate the mail merge by using the VBA in Microsoft Excel.