Multi-Line Text Vertical Alignment Centering

I am trying to center some text vertically and horizontally within a fillable text box on an editable PDF. I found out how to center the text horizontally, but I can't figure out how to center it vertically.

Here is an image of what I'm talking about.

The only way I've found so far to do something like this is to untick the box that says "multi-line", but obviously I need more than one line.

Could I do this with some scripting or is there an easier way?