[mannika]

Using the BINOMDIST function in Excel:

=BINOMDIST(2,26,1/3,1)= 0.002515
The above corresponds to the probability of a 1 or 2 occuring on only 2 or less of 26 dice.

Next, using the BINOMDIST function again to determine the probability of this happening x times over 100 rolls, we use:
=BINOMDIST(x,100,0.002515,0)

The value of this function for different x's:
p(0) = 0.777
p(1) = 0.196
p(2) = 0.025
p(3) = 0.002


The above probabilities correspond the probability of it happening x times over the 100 rolls. And in case you were interested, the expected number of times for it to happen is 0.2515 for each 100.