custom validation in angularJS

I am new to AngularJS.

In the following fiddle, when user clicks on "This submit triggers validation. But I wanted to put this button at the end of the page" button. I could see alert/error but I want to show a custom message, which I am struggling to do it.

Header inputs:
    <input type="name" ng-model="sample" required/>
    <input type="name" ng-model="sampleX" required/>

    <input type="submit" value="This submit triggers validation. But I wanted to put this button at the end of the page"/>
</form>

<hr/>

Some other form here. Think line items

<hr />
<a class="btn" ng-click="triggerSubmit()">Wanted this submit to trigger the validation to the form on which this button doesn't belong, e.g. trigger to header</a>

js fiddle link http://jsfiddle.net/unWF3/6/

Thanks,
Kalyan Basa