Upostha Sila in normal daily life I'm thinking of taking the upostha sila for 7 days targeting for a Pooja. And I am employed in a software engineering company so I'll be working for 5 days out of 7. 

Can you give me any advices on how to take the 8 preceps and how to protect them avoiding obstacles that could harm them during these working days? Some Sutta references are appreciated as well (if any)

-Metta
You might not be able to do this the traditional way.

But Sila is a promise to abstain. The promise can be to the Triple Gem of another person. Best is to make the promise to the Triple Gem.

Throughout the day recall the promise and see if you have broken it. If so take it again. If not make a determination to keep the posimie recollecting which precepts you have taken.

The skillful karma from the Sila is in the initial taking, recollection and retaking as well as the determination. So do the recollection retaking often with strong determination.

Also Sila has many level. Initially this can be like a rite or ritual. At an intermediate level it is based on Brahmavihara as breaking the precepts will harm or make other or oneself unhappy can cause negative karma for oneself, and at a higher level it is at level of sensation. The sensation is what gives arise to the unwholesome roots. So abstain from action which are unwholesome triggered by the respective sensation. More on this see: Kīta,giri Sutta.