It will be relevant to the statistics subject required to be completed by all b.comm students (quant. Methods 1), as well as introductory micro/macro-economics. The most commonly employed topics will include differentiation and probability (ie. normal distributions and binomial probability).
If you wish to complete an econ major - then calculus and probability becomes a major component of 2nd yr/3rd yr econ subjects. This is because econometrics is the study of the distribution of economic data; which requires the use of probability to estimate (ie. ols regression using a normal distribution curve). Also, microeconomics at university level is predominately the study of the marginal costs vs benefits of consumer choice and govt policies - which means that most economists have a hard-on for calculus.
If you wish to complete a finance major, then probability and statistics become a major part of your study. As asset pricing and financial modelling employs a lot from these 2 topics.
Having said this, dont be too freaked out when you start your b.comm course. Universities dont expect students to remember a lot from high school, so 1st yr is all about easing you back into education. I hadnt touched methods for 5 yrs before I went back to do my b.comm and I didnt find it very difficult. In fact, i believe that theats is fairly simple - its the concepts behind the maths that can be challenging.