All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
The dog's movement or lying down in some place does not restrict prayer therein, unless that place was touched by something of the dog's saliva, urine, feces or sweat, in which case the prayer would not be valid since the place's purity is a condition for the validity of the prayer.
Whoever prays in an unclean place and is mindful (of its impurity), then his prayer is invalid and he must repeat it. However, if he was ignorant of the impurity, and he is not aware of it until after his prayer, then he does not have to repeat it.
Also, if that impurity is removed by the sun or by wind or naturally changed into something else, then praying there becomes permissible.
It is established that Ibn ‘Umar said: "Dogs would come and go and urinate in the Masjid of the Messenger of Allaah, sallallaahu ‘alayhi wa sallam, and they (the people) would not put water on any of that." [Al-Bukhari]
It is known that if the impurity had remained, washing it would have been obligatory.
You could also take a mat with you to work, on which you could pray, if you cannot find a place that is pure.