vbscript read string in text file

Hello.  I was looking for assistance with an issue Im having with a script trying to read strings in a text file.  Shown below is the script.   Basically, it's looking for the existence of the filenames listed in the array, writes the file names that are found into a text file.  Then the script opens the text file with the file names, and if it finds the particular string in the file, writes a cooresponding number to another text file.  Then the script reads the numbers in that file and sets a variable to the numbers read, then uses that variable as the exit code.  I'm using this exit code for reporting in Altiris Notification Server.  Everything appeared to work fine, but then I noticed it would inconsistantly work or not work.  For example in the script, the first string to search is Test1.exe.  Even though the file is on the systems and the first part of the script writes this to the logfile, my InStr function isn't working and not reading this from the file.  Is there a way to have my string searches work consistantly?  Let me know if you can assist.  Thank you.

ON ERROR RESUME NEXT
strComputer      = "."
Const ForReading = 1

Set objFSO     = CreateObject("Scripting.FileSystemObject")
Set objLogFile = objFSO.CreateTextFile("LogFile.txt")
Set objRS      = objFSO.CreateTextFile("RSFile.txt")

arrFileNames   = Array("'Test1'","'Test2'","'Test3'","'Test4'")
strQueryFilter = "FileName = " & Join(arrFileNames, " OR FileName = ")

strComputer = "."
Set objWMIService = GetObject("winmgmts:\\" & strComputer & "\root\cimv2")
Set colFiles = objWMIService.ExecQuery("SELECT * FROM CIM_DataFile WHERE " & strQueryFilter,, 48)

For Each objFile In colFiles
   objLogFile.write(objFile.FileName & "." & objFile.Extension & vbCrLf)
Next

objLogFile.close

Set objLogFile = objFSO.OpenTextFile("LogFile.txt", 1)

 Do Until objLogFile.AtEndOfStream
   strSearchThis = strSearchThis & objLogFile.ReadLine
 loop

   if instr(strSearchThis, "Test1.exe") > 0 then
     objRS.Write "1"
   end if

   if instr(strSearchThis, "test2.dll") > 0 Then
     objRS.Write "2"
   end if

   if instr(strSearchThis, "test3.ocx") > 0 Then
     objRS.Write "3"
   end if

   if instr(strSearchThis, "test4.exe") > 0 Then
     objRS.Write "4"
   end if

objLogFile.close
objRS.close


Set objRS = objFSO.OpenTextFile("RSFile.txt", 1)

 Do until objRS.AtEndOfStream
   strResult = strResult & objRS.ReadLine
 loop

objRS.Close


If strResult = "" Then
   wscript.quit(0)
 Else
   wscript.quit(strResult)
End if