Can be very tricky, I'm sure you've found the ATANFULL commands already. ATANFULL will let you work out an angle from a height and length - so the Y angle should be straightforward. If you calculate the X and Z distance,, you have a method to calculate the X angle... ATANFULL(xb-xa,dist). The Z angle is roll, which you probably wouldn't want to use, or you'd probably want to handle roll differently.

So... calculate the difference between all values...

DX#=XA#-XB#

DY#=YA#-YB#

DZ#=ZA#-ZB#

Calculate XZ distance...

DXZ#=sqrt((DX#*DX#)+(DY#*DY#))

Calculate Y angle from XZ

AY#=atanfull(dx#,dz#)

Calculate X angle from DY

AX#=atanfull(dy#,DXZ#)

This is all untested, I could make an example for you, but I think you'll figure it out regardless - it's usually just that X angle that is tricky to calculate.

The code is dark and full of errors