Long Stay Visa in Schengen - for Business

[lfoltzccivalve]

I need to travel to Schengen countries for a business system implementation and will need to be in the region more than 90 days out of 180 days. This will be in and out time not a consecutive stay. I am struggling with the how to show requirements:

- Cover costs in area - should my company just provide a letter saying they are covering my expenses?

- Travel Document - what is this? a flight reservation? since my stay will not be consecutive I wont show a flight after the 90 days on my first trip. Can anyone advise/help on this?