Whether the install will go silently depends on the installer. For example, if it is using InstallShield, you can create a response file (setup.iss) by running setup.exe -r and then after copying the .iss file to the same folder as setup.exe, run setup.exe -s within your kix script.
code:
 $RC = MessageBox("Silent install will run now."
 + Chr(13) + "Please be patient!","ShowCase Strategy Install",64,60)
USE L: /DELETE
USE L: "\\FFSMS\SC3"
SHELL("L:\CLIENT\SETUP.EXE -S")

To prevent repeated installs on every logon you may check the registry for uninstall strings.
code:
 ;  check if already installed
$SC3uninstall = ReadValue("HKEY_LOCAL_MACHINE\software\microsoft\windows\currentversion\uninstall\ShowCase STRATEGY 3.0", "uninstallstring")
if $SC3uninstall = ""
  goto install
else
  goto finish
endif
_________________________
Give a man a fish and he will be back for more. Slap him with a fish and he will go away forever.