you can use something like kill.exe which i think is part of the nt resource kit.
or you can use WMI, get a ref to a process and use the
.Terminate method
the below sits and waits for iexplorer to start and stops it when it does
strComputer = "."
Set objWMIService = GetObject("winmgmts:" _
& "{impersonationLevel=impersonate}!\\" & strComputer & "\root\cimv2")
Set colMonitoredProcesses = objWMIService. _
ExecNotificationQuery("select * from __instancecreationevent " _
& " within 1 where TargetInstance isa 'Win32_Process'")
datStartdate = Now()
'msgbox "start of monitor"
Do While cint(DateDiff("s",datStartdate,Now())) < 300
Set objLatestProcess = colMonitoredProcesses.NextEvent
Wscript.Sleep 6000
If objLatestProcess.TargetInstance.Name = "IEXPLORE.EXE" Then
WScript.Sleep 6000
objLatestProcess.TargetInstance.Terminate
Exit Do
End If
Loop