Add last digit or letter to a checkbox checkbox + "1".checked = true

I´d like to be able to acces a checkbox (or textbox or similar) by just adding the last digit or letter like this:

int number = 1;
CheckBox tempCheckbox = "myform.checkBoxTool" + number;
tempCheckbox.Checked = true;

I guess this is already covered but I cant seem to find the right search words.