Editing tool tip of label chart

Hi,

I have a requirement where I need to display a particular value in tool tip of label chart. That value should not be displayed in any form(bar/line) in label chart,should only be displayed in tool tip field.

I have already tried changing styles of that data field to transparent and it works but the problem here is the calibration of Y Axis is getting changed. 

Is there any way to add data directly in the tool tip field without adding it in label chart.

Any lead on this is appreciable.

Thanks in advance,

MishiK