Gurushree

My husband has been advised to chant karya siddhi mantra or he can have karya siddhi yantra at home which would cost 11,000. Please advice me whether chanting the mantra or having the yantra will yield a good result soon. Please tell me the KARYA SIDDHI MANTRA that is meant for successful completion of official assignments and how many times it should be chanted daily. My husband is very much dejected as he gets series of reprimands from superiors inspite of diligent hard work. If this conditions prevails, he would have to search for another job. Please help me With regards Gurushree