Change "Display Title"

I have a form with a lot of select/drop down fields

Based on the user, I suspect many of the dropdowns will have only a single value to select, ie only one entry on the look up table
I want to default to this value if the lookup table has only 1 entry.

I could do this if I could programatically change the “Display Title” value on the look up dialogue.
I am opened to other solutions

Thanks

setup “Put de titile” NO, in that case the first value always is selected

Yes, but in that case it will ALWAYS show the first item.
I want it to do that under the condition that only one entry exists in the list.

yes, it is.
The other option is to assign the unique value in the onload event.

I have coded that so if there is only a single entry, display it. But thats cumbersome, was hoping for a single command somehow