here is the solution, you need to open the file first, find the line with the matching text, then re-open it and use a counter to stop before the desired line, then read it. MS could have made this so much easier!
Const ForReading = 1
strSearch = "PC123"
Set objFSO = CreateObject("Scripting.FileSystemObject")
Set objRegEx = CreateObject("VBScript.RegExp")
objRegEx.Pattern = strSearch
Set objFile = objFSO.OpenTextFile("c:\PC_DATA.txt", ForReading)
Do Until objFile.AtEndOfStream
strSearchString = objFile.ReadLine
Set colMatches = objRegEx.Execute(strSearchString)
If colMatches.Count > 0 Then
strLine2 = objFile.Line - 2
objFile.Close
Set objFile = objFSO.OpenTextFile("c:\PC_DATA.txt", ForReading)
For i = 1 to strLine2
objFile.ReadLine
Next
strLine3 = objFile.ReadLine
MsgBox strLine3
objFile.Close
Exit do
End If
Loop
objFile.Close