If I get it right you have a list of options like this:
<option> Mike </option>
<option> Steve </option>
<option> Joe </option>
And if user writes into input with id, id="drawingNo1" for example Joe everything is all right, but when he writes Adam it is wrong and you want to show error message?
If that is the case a recommend to use jQuery for this. I can write and example solution for you just let me know if I get it right. ;)
Here is the example:
http://codepen.io/xszaboj/pen/oXGOxG?editors=101[
^]