Open .TXT file Replace Specific Lines with Cell Values

Sub snb()
 sn=sheets("Sheet1").cells(5,1).currentregion
 
 for j=1 to ubound(sn)
  Open sn(j,1) For Input As #1
   sp = Split(Input(LOF(1), 1), vbcrfl)
  Close
    
  sp(8) = "whatever it has to be changed into"
  sp(9) = "I"

  Open sn(j,1) For Output As #1
   Print #1, Join(sp, vbCrLf)
  Close
 Next
End Sub