What is a good software that allows me to monitor my ads in Craigslist?

I run three ads for my computer repair business in Craigslist ,which are effective in bringing in business. However, due to Craigslist restrictions, I am limited to posting up to three or four ads at a time and I can only renew the ads only every two days. There is software available that allows me to work around this, allowing one to post more ads and re-posting these more frequently. I understand that this is possible mainly by renewing your ip address through use of this type of software. Can someone suggest the name of a free or low-cost software that is ideal for this purpose? I am struggling in my business and something like this would offer some relief.