You need an UDF (User Defined Function).
Paste the following code into a module.
Then you can use the syntax you described.

HTH
--
AP

'-------------------------
Function FILESIZE(fname As String) As Variant
On Error GoTo errHandler
FILESIZE = FileLen(fname)
Exit Function

errHandler:
FILESIZE = CVErr(xlErrNA)
End Function
'-----------------------------

"Mike McLellan" a écrit dans le
message de news: ...
Is there any way of determining the size of an external file from within a
spreadsheet? Ideally, what I would like to be able to do is something
like

IF(FILESIZE(filename)1000,do nothing,access file)