Here's another way.
' Read all lines into an array...
a = Split(objFSO.OpenTextFile(strDesktop & "\folder\blabla.vbs", ForReading).ReadAll, vbCrLf)
' Start with the 3rd line and read 28 lines (if available)...
For i = 2 To 29
If UBound(a) >= i Then strText = strText & a(i) & vbCrLf
Next