In a cell, show modified date for a linked document

Hello all,

I found, in another thread, the code for showing the modified date of a document in a cell, but I would like to take that a step further to show the modified date of a document from which I've linked data.

For example, I have 4 documents that contain funding information. Each document is updated many times throughout the day by different staff members. I created a "Daily Summary" document in which I linked the sums from the other 4, each on its own row, so that I can have a quick sum of all activity. The issue is that I haven't a clue if I'm looking at data from yesterday or from 10 minutes ago. Adding a 'modified date' for each of the 4 lines items in the summary would do that for me, but I don't know how to write the code.

The code to show the modified date of my "Daily Summary" document is:
"Private Sub Workbook_BeforeSave(ByVal SaveAsUI As Boolean, Cancel As Boolean)
Worksheets(""Sheet1"").Range(""E1"").Value = Now()
EndSub"

How would I amend it to show the modified date of the linked documents? I've tried playing around with the name of the worksheet, but I'm having no luck.

Any ideas would be appreciated!

Thanks,
Kay