How do i set only grid view to start on "day" timescale and stay on it unless changed in the timescale filter.

Good question, because you don't want it to prevent you from changing it to something other than day. Here's how...

1. Edit the script "Go To Calendar Tab ( Tab Name )" and find the step "Go to Object..."

2. After that step, add this:

If [ PatternCount ( $sc_Tab ; "Horizontal" )]
SetField [ CalendarInterface::TimeScaleGlob; "Day"]
Perform Script [ "Refresh Calendar { UseExistingData ; DontRefresh }"]
End If

That should get you the behavior you're looking for.

Hope it helps,

Many thanks, worked great...