Tell me about data validation custom formula?

How can I create my own data validation custom formula like in excel is this possible in libre calc not predefine I want my own how to make it?

You shouldn’t expect everybody to know how Excel does this and that (I last used it about 10 years ago, e.g.). Tell us what you want (giving relevant examples, best) and someone may suggest a solution. Sometimes Calc may open ways you didn’t know from some competitor’s software.