Similar to User Defined Fields you can also define your own User Defined Functions.
Assume you would like to change the upper/lower case of words, so that the first letter is in upper case and the other letters in lower case. For this you could define a function RightCase:
RightCase(x) lcase(left([x];1)) & lcase(mid([x]; 2))
You can use the new function like any other function now. For example this will return Raceresult:
RightCase("raCEreSuLt")
Functions can also have several parameters. As an example, define a function add:
add(x;y) [x]+[y]
The names of the parameters can be defined freely. When using them in the definition of the function, they have to be in square brackets.