I've three textboxes I want to convert to Double.

I don't know to use the IFormatProvider interface ...

Code:
				 // obtener los números desde el textbox
				 IFormatProvider* ifp;
				 Double a = A_coeff->Text->ToDouble(ifp);
				 Double b = B_coeff->Text->ToDouble(ifp);
				 Double c = C_coeff->Text->ToDouble(ifp);
The problem is in ToDouble(ifp).. that's causing an exception.

A_coeff, B_coeff and C_coeff are the textboxes.

Thanks!