Script to merge cells in columns and add text

Hi there,

I'm trying to modify columns in a table that represents a bus timetable.

My hope is to be able to create a script that will look for a minimum of three blank rows beneath a time value. If it detects this, I would like it to merge all the blank rows beneath the time value and above the next populated time value in that column, and add text "as per main timetable", shade the merged cells in a specific colour and rotate the text so it displays vertically.

Attached is an example of what I'm hoping to get close to. Attachment 30286

Any guidance would be greatly appreciated.