how to restrict order creation against under warranty machine based on user specific

Dear PM Guru's

i have one requirement in plant maintenance module, when i assign warranty dates in my equipment master data and when i am trying to create order against this under warranty machine, then based on configuration settings, it will show an information message as "Machine warranty will be expired on certain date" here i need an errror message against user specific and one more thing, on same machine, if authorized person tries to create order then system should allow to create order. Please guide me, what are the user exits are available to do this enhancement or development.

regards

JKM