g_unev

Please some one help!!!!!!!!!! :- :(

HI, I need to build a counter that is triggered by presence of a RF field in a particular area.For this a constant RF field transmitter(fixed at a place) has to be built. and also a portable RF receiver along with a counter circuit to count the no. of times I enter the RF field has to be designed. I am having trouble selecting the proper transmitter and receiver and the output formats. A detailed explanation for this project from you guys is expected. I want the whole model to come out very cheap.Your suggestions and help is needed. Regards, Venu Madhav