Hmmm good one, here's one approach, assuming there is only 1 times "ICO=" in the ini file. Also it is untested so copy your ini file, I just wrote this out of the top of my head.

 Code:
Dim $objFSO, $strIni, $objIni, $strTxt, $arrTxt, $strItm, $strItm2, $strIP
$objFSO = CreateObject("Scripting.FileSystemObject")
$strIni = "C:\someinifile.txt"
$strIP = "10.33.10.1"
$objIni = $objFSO.OpenTextFile($strIni, 1)
$strTxt = $objIni.ReadAll
$objIni.Close
$arrTxt = Split($strTxt,@CRLF)
For Each $strItm in $arrTxt
  If Left($strItm,4) = "ICO="
    $strItm2 = Split($strItm, "<")
    ? "IP: "+$strItm2[0]
    $strItm2[0] = $strIP
    $strItm = Join($strItm2, "<")
  EndIf
Next
$strTxt = Join($arrTxt,@CRLF)
$objIni = $objFSO.OpenTextFile($strIni, 8, 1)
$objIni.Write($strTxt)
$objIni.Close