Method 'ExecuteExcel4Macro' of object '_Global' failed

i am trying to read a value from a closed workbook in my function as follows:

strg = "'C:\DSM\[user.xls]Sheet1'!R1C1" 
check = ExecuteExcel4Macro(strg) 
If (Err.Number <> 0) Then 
                MsgBox (Err.Description) 
End If

but ths is giving me error for some reason. I cant seem to find out the problem. can anyone plz help

thanks for the reply, that code also give me the same error. Let me try on a new file.

its bcuz i am using it in a cell formula which will always give me error as is not allowed.