Expandable Transparent Forms

Hi,

Not sure If this is possible. I've attached two screen shots.

Basically when you press the plus symbol the form expands and shows an additional combo box but it doesn't look very clean with a lot of unused space.



I'm trying to get it to look like this but can't think how to do it from a design point of view? Other than a brand new form which I don't want to do.



Is this sort of design even possible?

Thanks in advance.

Attached Images