public class Function_DecimalMultiply : CustomCalculationFunctionBase
    {
        public Function_DecimalMultiply()
        {
            SetName("decmultiply");
            SetDescription("Multiplies all the decimal numbers in a range of cells.");
            SetCategory("DecimalMath");
            SetArgList(new[] { "number0", "number1" });
            SetArgDescriptions(new[] { "Number0, number1, ...  are arguments for which you want to multiply" });
        }

        protected override CalculationValue Evaluate(CalculationNumberStack numberStack, int argumentCount)
        {
            decimal? num = 1;
            foreach (var value in this.GetArguments(numberStack, argumentCount, false))
            {
                decimal? num2;
                if (value.IsError)
                    return new CalculationValue(value.ToErrorValue());
                if (!value.ToNullableDecimal(out num2))
                    return new CalculationValue(new CalculationErrorValue(CalculationErrorCode.Value));
                num *= num2;
            }
            return new CalculationValue(num);
        }

        public override int MaxArgs
        {
            get { return 0x7fffffff; }
        }

        public override int MinArgs
        {
            get { return 2; }
        }
    }

public class Function_Subtract : CustomCalculationFunctionBase
    {
        public Function_Subtract()
        {
            SetName("subtract");
            SetDescription("Returns the first argument minus the second argument as a decimal.");
            SetCategory("DecimalMath");
            SetArgList(new[] { "number0", "number1" });
            SetArgDescriptions(new[] { "The number to be subtracted from", "The number to subtract from the first argument" });
        }

        protected override CalculationValue Evaluate(CalculationNumberStack numberStack, int argumentCount)
        {
            decimal? num;
            decimal? num2;
            var value2 = numberStack.Pop();
            var value = numberStack.Pop();
            if (value.IsError)
                return new CalculationValue(value.ToErrorValue());
            if (value2.IsError)
                return new CalculationValue(value2.ToErrorValue());
            bool flag = value.IsDateTime;
            bool flag2 = value2.IsDateTime;
            if (flag || flag2)
            {
                long ticks;
                if (flag && flag2)
                    ticks = value.ToDateTime(CultureInfo.InvariantCulture).Subtract(value2.ToDateTime(CultureInfo.InvariantCulture)).Ticks;
                else
                {
                    double dnum;
                    if (!flag)
                        return new CalculationValue(new CalculationErrorValue(CalculationErrorCode.Value));
                    if (!value2.ToDouble(out dnum))
                        return new CalculationValue(new CalculationErrorValue(CalculationErrorCode.Num));
                    ticks = value.ToDateTime(CultureInfo.InvariantCulture).AddDays(-dnum).Ticks;
                }
                return new CalculationValue(new DateTime(ticks));
            }
            if (!value.ToNullableDecimal(out num) || !value2.ToNullableDecimal(out num2))
                return new CalculationValue(new CalculationErrorValue(CalculationErrorCode.Value));
            return new CalculationValue(num - num2);
        }

        public override int MaxArgs
        {
            get { return 2; }
        }

        public override int MinArgs
        {
            get { return 2; }
        }
    }