setField(fieldName as String, value as Object) as Boolean
Sets the value of the subject node field identified by fieldName to value. This will fail and stop script execution if the value is not of the appropriate type. Returns true if the field is successfully set, false otherwise.
isFieldSet = m.top.setField("someField", someString)
print "isFieldSet: "; isFieldSet
So, I'm as sure as I can be.