Scripting in bCNC

[massiveradiation]

Hey folks,
I'm trying to figure out basic scripting in bCNC. I've got a probing routine that I copied from somewhere else and everything works, assigning variables hard numbers and it runs until it gets to the formula part, where it needs to take probe data and compute center of circle. I tried putting all variables in brackets, but that didn't work. Same behavior, new XY "cx, cy" is not changed from original position. So the command G0 X[cx] Y[cy] sends back to XY coordinates I had set before starting the code.
Any help would be appreciated. I'm not much of a coder, but I'd love to learn. I think it's either a syntax problem or maybe bCNC won't allow calculations? Not sure.
Thanks in advance!
Below is all of the code, which probes inside of a bore to find bore's center, then probes top.
Tyler

;Start with probe in hole, BELOW Z surface

; Wait until the planner queue is empty
%wait

; Set user-defined variables
%PROBE_DISTANCE = 10
%PROBE_FEEDRATE_A = 150
%PROBE_FEEDRATE_B = 50
%HOLE_DEPTH = 3
%PLATE_THICKNESS = 2.75

; for restoration at the end
%UNITS=modal.units
%DISTANCE=modal.distance

G91 ; Relative positioning
G21 ; Use millimeters

G10 L20 X0 Y0 ; set current position as xy zero for now

; Probe rear, slight right
G38.2 X1 Y[PROBE_DISTANCE] F[PROBE_FEEDRATE_A]
G1 Y-1 F[PROBE_FEEDRATE_B] ; back off a bit
G38.2 Y3 F[PROBE_FEEDRATE_B] ; probe again, slowly
G4 P1 ; wait for 1 second to ensure clear and accurate measure
%p1x = posx ; set the x/y coords for later
%p1y = posy

; set back to absolute mode and return to original spot
G90
G0 X0 Y0
G91

; Probe 45deg
G38.2 X[PROBE_DISTANCE] Y[PROBE_DISTANCE] F[PROBE_FEEDRATE_A]
G1 X-1 Y-1 F[PROBE_FEEDRATE_B] ; back off a bit
G38.2 X3 Y3 F[PROBE_FEEDRATE_B] ; probe again, slowly
G4 P1 ; wait for 1 second to ensure clear and accurate measure
%p2x = posx ; set the x/y coords for later
%p2y = posy

; set back to absolute mode and return to original spot
G90
G0 X0 Y0
G91

; Probe slight rear, far right
G38.2 X[PROBE_DISTANCE] Y1 F[PROBE_FEEDRATE_A]
G1 X-1 F[PROBE_FEEDRATE_B] ; back off a bit
G38.2 X3 F[PROBE_FEEDRATE_B] ; probe again, slowly
G4 P1 ; wait for 1 second to ensure clear and accurate measure
%p3x = posx ; set the x/y coords for later
%p3y = posy

; Figure out proper center https://stackoverflow.com/a/30106470 and set it
%ma = (p2y - p1y) / (p2x - p1x)
%mb = (p3y - p2y) / (p3x - p2x)
%cx = (ma * mb * (p1y - p3y) + mb * (p1x + p2x) - ma * (p2x + p3x)) / (2 * (mb - ma))
%cy = (-1 / ma) * (cx - (p1x + p2x) * 0.5) + (p1y + p2y) * 0.5

; Return to origin, move to true center, wait, set zero
G90
G0 X0 Y0
G91
G0 X[cx] Y[cy]
G4 P1
G10 L20 X0 Y0

; Move up over the top, up and right to get over metal, probe down twice (quick, then slow) to get z height
G0 Z[HOLE_DEPTH]
G0 X15 Y15
G38.2 Z-25 F[PROBE_FEEDRATE_A] ;Fast Probe
G1 Z1 F[PROBE_FEEDRATE_B]
G38.2 Z-5 F[PROBE_FEEDRATE_B] ;Slow Probe
G10 L20 P1 Z[PLATE_THICKNESS]

; Move back up and over to the XY
G0 Z5
M6 ; Remove the probe
; Rapid back to zero for validation
G90 ; absolute positioning
G0 X0 Y0
G0 Z0

[UNITS] [DISTANCE] ;restore unit and distance modal state