How to give error message for the screen element text field when wrong i/p

How to give error message for the screen element text field when wrong i/p

when wrong input given

eg.

I have a text box with SBOOK-CARRID

so when user give wrong entry in text box i.e LG

then I should give some error stating that the the input is invalid or not available ,

now it showing the error of standard messages,

i want manual message to be displayed when error comes.

Thank you,

Regards,

Jagrut Bharatkumar Shukla