User friendly differential equation solver

This is kind of hard to explain.

I am creating a numerical solver that gets input from students in the form of an equation. An example being x^2 + y^2. I'd like to take this input and somehow put it into VBA as is.

This equation is going to be in a for each loop, where the values of x and y are changing with each iteration.

For i = 1 To n
m = x^2 + y^2 'Equation input from students
y1 = y + m * dx
y = y1
x = x + dx
Next i

I pretty much need to paste the input from the students into the m variable, where x and y are declared variables as well.

Is this even possible? Variables within a string.


User friendly differential equation solver

Have you already done the solver? If not, tell me please, can you use the cells of excel worksheet and what is the way of student's input of an equation? I'll try to help