You really do not need an online calculator.
You should be looking at the difference in the interest charged and not the difference in the repayments.
You should be looking at it on an annual basis or maybe looking at 3 years, but no more. You can switch if another lender becomes cheaper.
The difference between 3.58% and 3.17% is 0.4%
For a mortgage of €100,000, 4% is €4,000, so 0.4% is €400
So, you will save €400 per €100,000 per year if you get this lower rate.
Brendan