This tech doc provides a simple js script solution.
Release : 17.3
myfield_onChange : function() {
var the-val = ca_fdGetTextFieldValue(formId,"myfield");
var NotAllowed = ["string1","string2","string3"]
if(NotAllowed.indexOf(the-val) != -1)
if (NotAllowed.indexOf(the-val)+1) {
ca_fdSetTextFieldValue(formId, "myfield","")
alert(the-val + " is not allowed, please choose enter again.");
}
},
***note: the field name is myfield***