check if textInput.focus == true?

How can I check if the focus is on a particular textfield?

I want to make a statement like below (though preferably a working one :) ), the code should only be executed when the focus is not the field:

if ( myForm.textInput.focus != true )
{
task
}

Just do
myForm.textInput.onfocus = function()
{
task
}
or put onfocus="doSomething()" in the actual input box.