🚀 go-pugleaf

I have an Aplication that draws a map based on 16X16 'Shapes'
These shapes are stored in their own Bitmap.
To Draw the map I Loop through Each square calling BltBitMap to copy
from my shape bitmap into the screen bitmap.

The problem:  

Each square contains Terrain(one of several shapes)
as well as A potentially a unit(Represented by another set
of shapes(Again All in the same bitmap)
To draw each squre currently involves 3 calls to
BltBitMap. 1 to draw terrain, 2) to 'zero out' the pixels for the unit
(By using a all 1's mask in the shape of the unit shape(Basically a
cookie cut with no save)) and 3 draw the unit into the square. The net
result is to overlay the unit on the terrain.
What I need/want is a way to do this with a single function..I don't think
any of the stock functions will handle it, and I was
just wondering if Any one code supply some code that would (Aztec 3.6 or
even better an assembly routine that does it all in one Blit)
					Thanxs in Advance for any help
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