Dollar cost averaging

Hello all, I'm new to investing and haven't put a single dollar into the market yet but I have saved some cash and I'm looking to invest soon. I've read a few books and learnt heaps but just need a question answered.

so the question is - can I use the dollar cost averaging system through commsec? Will it charge me a 20$ fee everytime I invest? 

im looking to start with asx:VAS and want to start with $1000-3000 initially and then every month after that add in $100-200 but unsure if I'll get charged $20 fee everytime?

thankyou for reading!