I understand what you mean, but your example is absolutely useless. I found no vasm syntax- or cpu-module which accepts only parts of that source.
Probably you are working with "std" or "oldstyle" syntax, as those are the only syntax modules which accept named macro arguments. But in this case all arguments have to be preceded by a backslash character ('\').
And there is already a solution to your problem. "\()" may be used to separate macro arguments from the following code. So in your case it should be:
Code:
z80word (\Sample\()_End-1)|$8000