Vlookup auto-update from another file

Hello,

I have this formula here:

=IFERROR(VLOOKUP(T15,INDIRECT(CONCATENATE("'C:\Documents and Settings\[",$C$7,".xls]",$C$6,"'!$E$3:$S$200")),11,FALSE),0)

The main function of this formula is a vlookup function on a specific file to a specific worksheet.

$C$7 = specifies the name of the file
$C$6 = specifies the name of the worksheet in that specific file

The issue I have been having is that the formula is unable to extract the vlookup information, unless I have the specific file open. Are there ways around this issue? Perhaps a different formula?

Sincerely,
xHaxelx