Had a quick look at your sample. You have mouse button and push button mixed together with an action event.
For ‘mouse’ left, right, middle, single, double clicks examine my mouse event. oEvent contains results if you examine with a tool such as MRI.
Another item to see → Creating Event Listeners
Unfortunately that modified version still kicks me out at the same line.
Must have goofed up again. It occurs a few times. Just delete the line(s). Will clean it again & post corrected copy.
.
Edit:
’
Post now has corrected version noted as corrected version
It works! You got it!! 
I noticed the columns repeat themselves, when you scroll to the right, is that part of the workaround? Not the end of the world, at all, just curious.
Before I plunge in all the modifications you have done, I want to read again Mr. Pitonyak’s chapters 10 through 13. Every time I look at this text, as well as “Useful Macro Information” I find yet something I missed before. Either way I will mark this thread as resolved, because you got it to the point where it truly is. And I’ll post future questions in new threads so that folks can subsequently refer to them, looking for answers. Once again, thank you very much for your time and your input. There is no way I could have done this on my own with my limited knowledge of this craft and time available.
No. another missed item I need to correct again. There columns are input twice. Give me 5 minutes & will fix.
Edit: fixed columns and horizontal scroll gone and grid larger.
@marus_b this is related → UNO Grid Control
deleted intentional
I had similar problem to Problem #1.
The difference was that my ControlGrid was created statically on dialog, thus I hadn’t to create the model programically:
oModel = createUnoService("com.sun.star.awt.grid.UnoControlGridModel")
but only get this object by:
oModel = oGridControl.getModel()
so the code looked like:
Dim oDataModel As Object
oDataModel = createUnoService("com.sun.star.awt.grid.DefaultGridDataModel")
Dim oModel As Object
oModel = oGridControl.getModel() ' just get model, not create
'oModel.ColumnModel = oColumnModel
oModel.GridDataModel = oDataModel
oModel.ShowColumnHeader = True
The code worked, but had Problem #1.
The solution I found is to re-set the model after modifications:
Dim oDataModel As Object
oDataModel = createUnoService("com.sun.star.awt.grid.DefaultGridDataModel")
Dim oModel As Object
oModel = oGridControl.getModel() ' just get model, not create
'oModel.ColumnModel = oColumnModel
oModel.GridDataModel = oDataModel
oModel.ShowColumnHeader = True
oGridControl.setModel(oModel) ' <--------
and Problem #1 has gone.