Found it...
Here is the code I used:
Function Update( source, target )
Dim f1,f2,d1,d2,c1,c2
If fs.FileExists( source ) then
set f1 = fs.GetFile( source )
d1 = f1.DateLastModified
c1 = Year(d1) * 10000 + Month(d1) * 100 + Day(d1)
If fs.FileExists( target ) then...