If it's just a single cell that has that hyperlink...
Format the cell nicely -- make it look like a hyperlink (but make sure you
remove any existing hyperlink).
Now show the Drawing toolbar
View|Toolbars
in xl2003 menus
Place a rectangle over that cell so that it covers the text you want to make
look like a hyperlink.
You can hide the borders so that it looks pretty later.
Now hit alt-f11 (to get to the VBE, where macros live).
Click on Insert|Module on the VBE's toolbar.
Paste this into the newly opened Code window -- usually on the right hand side:
Option Explicit
Sub LoadPDFs()
ThisWorkbook.FollowHyperlink "C:\my documents\firstfile.pdf"
ThisWorkbook.FollowHyperlink "C:\my documents\secondfile.pdf"
End Sub
You'll have to change the path and filename for both files.
Now hit alt-f11 to get back to excel.
Rightclick on the rectangle and choose Assign macro
Point at LoadPDFs
and click ok
Then test it.
If it works, then it's time to hide the borders of the rectangle (if you want).
Rightclick on the rectangle
choose Format|autoshape