Conditional Formatting in Excel 2016

I have a worksheet that I have successfully added conditional formatting rules, circa 25+! For example, in col A I have a rows (approx. 800) of dates (Jan to Dec). Each row, based on other criteria in another column, I can give a different colour to or underline when the day changes. This all works ok.

However, when I add another row (and I will need to) the conditional formatting then appears to add more conditional formatting rules for that cell / row etc. and I therefore end up with a very large number of conditional formatting rules when all I need is the original set of around 25+.

Is there a way of 'stopping' the conditional formatting process adding these extra rules or is there a different approach for me to adopt when creating these rules?

I hope the above makes sense and thank you for your help.

Ford, thank you for a quick response. Unfortunately I am not experienced with VBA and therefore not familiar with the terms you use of; code tags, /code, or use the #button.