Is not a custom tooltip... It a custom itemeditor in the datagrid.
This itemeditor is a textinput with a validator.
When the text change the validator validate and show a red border with
a tooltip... Something like this
<mx:TextInput x="50" y="21" width="208" creationComplete="doInit()" >
<![CDATA[
import mx.controls.dataGridClasses.DataGridListData;
import mx.validators.EmailValidator;
import mx.validators.DateValidator;
import mx.core.UIComponent;
import mx.managers.FocusManager;
import mx.controls.Alert;
import mx.events.ValidationResultEvent;
import com.timeline.validators.HistoryDateValidator;
import com.timeline.model.CustomDate
public var validator:HistoryDateValidator= new HistoryDateValidator();
private function doInit():void {
validator.source= this
validator.property="text";
validator.addEventListener(ValidationResultEvent.VALID,handleResult)
validator.addEventListener(ValidationResultEvent.INVALID,handleResult)
validator.trigger=this;
validator.triggerEvent ="change";
validator.validate();
}
</mx:TextInput>