Mail Merge of Excel data to Word

I have excel data in different sheets that I need to merge into word documents and they are split in three sheets corresponding to 3 different word templates. I also need to program a logic for combination of any number of documents of each type and excel records are organised already in an aligned structure with the same initial row in each of the 3 sheets for the same record while the maximum row between sheets is saved and the next record is strategically placed on the next empty row (maxrow of previous record + 1). I already have a method of saving counts of documents in respective sheets and  row pointers that helps the merge program find the record to merge ..
When all the documents in a combination record are created they need to be saved as a unique filename whose string is saved automatically in one of the excel fields in each different sheet. and all these word documents are saved in an output folder at a predetermined location