Custom ToolTips, active when there is data only available

Hi

Is it possible to control when a tooltip works or only activates when there is related data available? 

I have created a custom tooltip - see screen print, which provides additional staff information if it exists in another small table in my model.  When you pass over some of these rows, on the main visual, I just a get blank box or at least a box with the headers I dfines as there is no related data there.  Is there a means to allow the tooltip to appear only if there is any data/record in the source table for that row?  (thinking along ghe lines of a mouse-over but only shows details if they exist)

Or is there another method/approach I could consider instead?

ToolTipStaf Details

Many thanks

Chris