"Right now it is easier to write a function in all assembler than fight through .SRC and all that stuff."

Using ".SRC and all that stuff." means that you lose all 'C' source-level debugging for the whole file

Therefore I agree with Erik: it's far better to write your function in Assembler than to use Keil's inline assembler in 'C' :-(

However, Erik would also suggest that the SRC directive is an excellent way to start your assembler function - getting the Compiler to create a template for you.