I'm writing an app in VB with an excel worksheet. At one point I need to solve a set of equations that are not explicit, so I need a numerical solver program. Excel's Solver is supposedly designed for this purpose; however my past experience is that it is very fickle and prone to problems. So my plan is to find another (preferably free) numerical solver program out there that can interface with Excel and/or Visual Basic. I was wondering if anyone has tried this before and can recommend a program or solution?