I will be working in Kathmandu for the next few weeks (07:00-18:00) job. Can anyone shed some light on some must things to do in Kathmandu while I am here?

No I do not need work in Kathmandu. Just want to know what there is to do while I am working in the city. Hopefully there will be time for a roadtrip or two before I leave.
Cheers.
There are 5 World Heritage sites right in the City of Kathmandu and it's neibhbour, Patan plus 2 in the surrounding valley - Bhakapur (13 km east) and Changu Narayan Temple, just north of Bhaktapur a few km. Nagarkot, a hill village on the eastern valley rim, is a quite, relaxing place to visit with good views on a clear day of the Kathmandu Valley, hills, ridges and main main range of the Himalaya on a clear day. Combining Nagarkot with a visit to Bhaktapur and Changu Narayan makes a nice weekend trip overnighting at either Nagarkot or Bhaktapur. If you have a day or two more to spare, climb up to Chisopani from Sundarjal and stay overnight (wonderful sunrises from here) and then walk to Nagarkot next day. Following day walk to Dhulikhel, then onto Namo Buddha and Bhaltahli over the next 3 days. End up with a short walk down to Panauti and take a bus back to Kathmandu. Or you can go out to the Botanical Gardens at Godavari in the south part of the valley or visit the old villages of Thimi, Kitipur or Sanku or Chobar Gorge or the Dachinkhali Temple....and those are just starters - you haven't even left the valley yet.
Go into Pilgrims Book Store and get yourself a Guide Book - there is one just for the City and Valley area - lots of corners to poke into and enjoy. Hope you won't be just an observer as it is much more interesting when you know a bit of the history of what you are looking at!