If the trademark you planned to use is similar to a registered mark or senior mark, it is unlikely that you can use your proposed trademark in the same category of goods or service. To infringe an existing trademark, the junior mark does not have to be exactly same as the existing mark. As long as they look alike or sound alike, your trademark will be likely to cause the consumer's confusion of the source of the goods. However, the evaluation of the likelihood of confusion involves many factors and legal interpretations. Therefore, you should contact an intellectual property attorney to issue an opinion letter of your proposed trademark.