I have obtained a Solver extension at

Roundtrip to Shanghai via Tokyo » Calc Optimization Solver

I was surprised to see that it only minimizes or maximizes instead of having another option to make an objective function converge to a given value... I found a workaround:

To make f(x) converge to a value A, I make another cell with abs(f(x) - A) and minimize that cell by using solver.

It is incredible how such a stupid problem can be solved by thinking about it...

I also added an statistics extension to Calc (R4calc) but haven't tested it yet...