Copying Filename While Merging Workbooks?

I have a few hundred workbooks that I am merging into a single file. I found the following vba code that performed this task very well.

Sub simpleXlsMerger()
Dim bookList As Workbook
Dim mergeObj As Object, dirObj As Object, filesObj As Object, everyObj As Object[code]....

After I merged the data, I realized that I needed to know the source file that each row of information comes from.

How can I modify the above script to copy the filename and add it as an additional column of information when each sheet is copied into the master file?

For Example:
Currently If I have 3 files:
File 1:
1 2 3
4 5 6
File 2:
a b c
d e f
File 3:
v w x
y a b

Running what I currently have will give me:
1 2 3
4 5 6
a b c
d e f
v w x
y a b