Take a look at the header ofIsInIPRange()
quote:

;REMARKS This function is deprecated in favor of IsInSubnet() at
; http://www.kixtart.org/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=12&t=000053
code:
Call "isinsubnet.udf"

$ipaddress = @IPADDRESS0

Select
Case isinsubnet($ipaddress,'10.125.16.0/20') 
  $spserver='jcboe'
Case isinsubnet($ipaddress,'10.125.32.0/20')
  $spserver='alt'
case 1
  $spserver='no match'
EndSelect 
? 'Error '+@ERROR+' - '+@SERROR
$SPAlert = MessageBox($spserver, "Simple Test", 64, 60)
_________________________
There are two types of vessels, submarines and targets.