Something like this maybe:
 Code:
Shell 'osdenv.exe /Regserver'
If @ERROR "Failed to register OSDENV: ["+@ERROR+"] "+@SERROR+@CRLF Exit @ERROR EndIf
$objOSD = CreateObject("OSD.Environment")
If 9<>VarType($objOSD) "Cannot create OSD object: ["+@ERROR+"] "+@SERROR+@CRLF Exit @ERROR EndIf
$objOSD.OSDMP = "SMS1:80"
$objOSD.OSDSITECODE = "PS1"
Shell 'OSDSWDExec.exe "PS100001:PER-SYSTEM UNATTENDED INSTALL 1" MSIEXEC.EXE /I BRXTEMPLATESC14.MSI /QB!-'
If @ERROR "Failed to execute OSDSWDExec.exe: ["+@ERROR+"] "+@SERROR+@CRLF Exit @ERROR EndIf