infotype enhancement using BADI

Hi all,

this naresh,

i am new to BADI and all Enhancement except PM01.

i got a requirement that infotype 0019 enhancement using badi.

i got the badi HRPAD00INFTY.

i need to populate a mesage after user enter data ex: request for leaves, if employee is in prohibition period then i should need to raise an error message specifying - you are in prohibition period and not eligible for leaves.

can any1 share entire code that need to be written in PAI.?

thanks,

naresh.