Const ForReading = 1, ForWriting = 2, ForAppending = 8
Const TristateUseDefault = -2, TristateTrue = -1, TristateFalse = 0
Dim fso, FileName, TextLine, Tempfile, inTempfile, strPath, Temp, intemp
FileName = "C:\Users\rahul\Desktop\PLR\1.rtf"
TempFile = "C:\Users\rahul\Desktop\PLR\Temp\1.txt"
Set fso = CreateObject("Scripting.FileSystemObject")
Set inFile = fso.OpenTextFile(FileName)
Do While inFile.AtEndOfStream <> True
    TextLine = inFile.ReadAll
Loop
Set regEx_ = new regExp
With regEx_
    .Global = True
    .MultiLine = True
    .IgnoreCase = True
    .Pattern = "\{\\\w{4}\\\w{4}\\\w{11}"
TextLine = regEx_.replace(TextLine, "mmrk$&")
'many such find and replace to get IMP lines Having mmrk
End with
set Temp = fso.CreateTextFile(TempFile, True)
    Temp.Write TextLine
    Temp.Close
Set Temp = Nothing

Set intemp = CreateObject("Scripting.FileSystemObject").OpenTextFile("C:\Users\rahul\Desktop\PLR\Temp\1.txt")
Set outFile = CreateObject("Scripting.FileSystemObject").CreateTextFile("C:\Users\rahul\Desktop\PLR\Temp\11.txt",True)

Do Until intemp.AtEndOfStream
    Dim line : line = intemp.Readline
    If Left(line, 4) = "mmrk" then outFile.writeLine(line)
Loop

intemp.Close
outFile.Close
inFile.Close