Add Text To Cell If Blank

Im working on creating a search box. In the box the user will input text, when the cell is blank, i would like it to say "WUC or Nomenclature". and once they select the cell, and start typing it removes (which is how excel works anyways) Cell D3 is the search box. While trying to figure this out on my own I have came to the simple formula of

Code:

=IF(D3,"","WUC")

in (H3). Which creates the effect I desire but in the wrong cell. I've tried applying this to conditional formatting but Im not sure if conditional formatting is designed for this purpose. Not sure if its even possible using forumulas. Perhaps using VBA, but we have limitations on VBA on our work computers and while I can do some, the end users have to enable it, which they never remember to do.