MergeWorkbook Method
Merges changes from one workbook into an open workbook.
expression.MergeWorkbook(Filename)
expression Required. An expression that returns a Workbook object.
Filename Required String. The file name of the workbook that contains the changes to be merged into the open workbook.
Example
This example merges changes from Book1.xls into the active workbook.
ActiveWorkbook.MergeWorkbook "Book1.xls"