Modifying Employment Agreements?

An anonymous reader asks: "I am starting a new job, after months of unemployment. While out of work, I started a technology related business. I do not believe there is a conflict in the services provided by this business and the job I am taking. As has been standard with previous employers, I have been asked to sign an agreement that states in part that I am to disclose to the company anything that I create wether or not during company time, and wether or not it relates to the company. I also must agree that these same creations or inventions become the sole property of the company. I would like to change the wording to only include those creations, inventions and other Intellectual Property that is the direct result of work performed for the company, involved use of company property, and/or was created or invented during paid hours spent working for the company. What success or failure have other Slashdot readers had when dealing with wide reaching employment agreements such as this? How did you approach management with your modifications?"