In this study we show the models that students of administration and accounting careers built when performing an activity close to the real life, with the use of Excel. The representations and ideas exhibited by the students when they used the software are analyzed. The methodology was qualitative. The theoretical framework was the Models and Modeling Perspective. The results show that the use of the tool allowed the dynamic exploration of mathematical concepts such as: covariation, rate of change and exponential function. The students formulated conjectures, arguments, explanations and justifications. [For the complete proceedings, see ED606556.]