>I wanted to share a further improvement on this that I finally discovered. One of the remaining issues was that setting the ToolTipText= "" does not turn off the displayed tooltip immediately as it would normally when you move off of an item. So to get the ToolTip display to go away as soon as the cursor is moved off of the grid column, you can do the following. (Good ole INKEY() to the rescue again). I couldn't find any other way to make this work without using INKEY().
>
>-Mark

Next version...

* Add new property ToolTipSource with value "Header1" to class Column

* Add this to the Column.MouseLeave event
LOCAL lcCur,llST
This.Parent.ToolTipText= ""
lcCur=SET("CURSOR")
SET CURSOR OFF
llST=Thisform.ShowTips
Thisform.ShowTips= .F.  && now turn off currently displayed tip
INKEY(.1)
Thisform.ShowTips= llST
SET CURSOR &lcCur.

* Add this to the Column.MouseEnter event, (as Andreas provided).
IF EMPTY(This.ToolTipSource)
   This.Parent.ToolTipText= This.ToolTipText
ELSE
   This.Parent.ToolTipText= EVALUATE("This."+This.ToolTipSource+".ToolTipText")
ENDIF

* Add this to the object/class Header.MouseLeave event
This.Parent.MouseLeave(nButton, nShift, nXCoord, nYCoord)

* Add this to the object/class Header.MouseEnter event
This.Parent.MouseEnter(nButton, nShift, nXCoord, nYCoord)