What function I have to use?

Hello to All!!!
What function I'd have to use, if I want:

I have simple variable
myvar = "I have a dog, cat"

I want to change "myvar" to myvar="I have a dog"
BUT I want to achieve this result without using "replace" functions because I don't want to input replace strings
I just want to put only strings, that I have to DELETE from myvar, so I don't want to use "substring2"
In ideal, the function can look like:
function(string, "value for deleting from string")
Does CF8 has a function like this???

Thanks for your answers!!!