Validating a value based on a functions

I created a function that basically is a an array that associates a numerical value to a string

function myValidation(mip)

{

var text = "";

var mipCodes = {
"A100" : "String 1",
"A101" : "String 2",
"A102" : "String 3",
"A103" : "String 4",
"A104" : "String 5"

}

//When a MIP code is entered
if (mip != "") text = mipCodes[mip];

return text;
}

I want to use this function as a validation script, like if the function return an empty string (meaning the value was not found in the array), the value is not commited.

I tried this validation script:

if (text == "") event.rc = false;

When this will work, I'll need to add other validation functions in a row before a value is commited.