I have couple of polygon layers that i want to fill the blank spots automatically can anyone please help me?
Not entirely sure what you mean. You say 'fill' which I think of as filling gaps/holes in a polygon, but you state 'marking outside polygon layer' which makes me think otherwise.
Do you have a screenshot or can you explain it better?
If you create a geodatabase topology in a feature dataset with the "Must Not Have Gaps" topology rule, this would find those errors and provide solutions
Try Union tool with Allow Gaps option:
"The Allow Gaps parameter can be used with the All attributes or Only feature IDs settings on the JoinAttributes parameter. This allows for identification of resulting areas that are completely enclosed by the resulting polygons. The FID attributes for these gap features will all be -1."
Then select the gap polygons (FID = -1), run Eliminate tool to merge these polygons into neighboring polygons by largest area or longest shared border.