Hi,
Thank you both for the replies. I've been reading and re-reading them....
I can do what the gif shows already... I think, unless I'm missing something.
You know when you're filling in a form on a web site and there are pre-populated values in some fields? Then when you click on a field, the pre-populated value is selected so that if you start typing the pre-existing value is overwritten?
I want to select the value in the label or textinput when the label or textinput receives the focus.

This is a form I found on the internet. The form flow is backwards but it shows what I mean. The focus moves from the yellow drop down to the Text: field. When I do a Shift+Alt+Tab the focus move up to the Text: field and the value that is existing in the text box is selected.
Therefore, in my app I want to select a value from my dropdown. Once I do that, the lookup sets the value of my label and then the focus is set to the label. When the label receives the focus I would like the value to be selected just like "Test" is selected in the gif above.
Am I doing any better explaining? I hope so. Thank you for your patience.