Excel Formula Help

I'm really not sure how I can write this out, but basically what I want is one cell to say

=if(E193>0, E193-E135,"")

then the next cell to say
=if(E194>0, E194-E135,"")

and be able to drag it down and keep the E135. Whenever I drag it down to apply the formula to the other cells, it will go up to E136 and so forth. How do I get the E135 to stay in all of the cells but have the E194 go to E195?