A* help!

well, i fixed the TYPO, but now I appear to be having logic flaws (?)
kinda hard to explain, cause I have NO idea what's going on.

Graphics3D 1280, 1024, 32, 1

Const gridscale = 1
Global goalx, goaly, startx, starty
Global currentx, currenty

Global lf = 10000000000

startx = 300
starty = 300
currentx = startx
currenty = starty
goalx = 800
goaly = 600


Type goodnode
	Field x
	Field y
	Field open = False 

End Type

Type badnode
	Field x
	Field y
End Type

Type potentialnode
	Field x
	Field y
	Field g
	Field h
	Field lf
End Type

Type hlnode
	Field x
	Field y
End Type


setupgrid()


While Not KeyHit(1)
	Cls()
	RenderWorld()
	drawgrid()
	

	
	If KeyDown(29) Then
		Stop 
	EndIf
	
	If KeyHit(57) Then updatepath()
	Flip()

Wend


End

Function setupgrid()
	For w = 0 To GraphicsWidth()-(gridscale*100) Step gridscale*100
		For h = 0 To GraphicsHeight()-(gridscale*100) Step gridscale*100
			node.goodnode = New goodnode
			node\x = w
			node\y = h 
		Next
	Next
End Function

Function drawgrid()
	Color 0, 0, 200
	For node.goodnode = Each goodnode
		Rect node\x, node\y, gridscale*100, gridscale*100, 0
	Next
	Color 0, 200, 0
	For hnode.hlnode = Each hlnode
		Rect hnode\x, hnode\y, gridscale*100, gridscale*100, 0
	Next
	Color 255, 255, 255
End Function 

;g = 10 if vertical or horizontal
;g = 14 if diagonal

;h = 10*(abs(currentx - goalx) + abs(currenty - goaly))


Function updatepath()
	Repeat
	Cls
	RenderWorld()
	 
		If KeyHit(29) Then Stop 
		Text 0, 0, currentx + ", " + currenty

		;find the surrounding 8 nodes and replace them with potentialnodes (closing the normal ones)
		For node.goodnode = Each goodnode
			If ((node\x = currentx - (gridscale*100)) And (node\y = currenty)) Or ((node\x = currentx) + (gridscale*100) And (node\y = currenty)) Or ((node\y = currenty - (gridscale*100)) And (node\x = currentx)) Or ((node\y = currenty + (gridscale*100)) And (node\x = currentx)) Then 
				pnode.potentialnode = New potentialnode
				pnode\x = node\x
				pnode\y = node\y
				pnode\g = 10
				node\open = False  
			EndIf
			If ((node\x = currentx + (gridscale*100)) And (node\y = currenty + (gridscale*100))) Or ((node\x = currentx + (gridscale*100)) And (node\y = currenty - (gridscale*100))) Or ((node\x = currentx - (gridscale*100)) And (node\y = currenty + (gridscale*100))) Or ((node\x = currentx - (gridscale*100)) And (node\y = currenty - (gridscale*100))) Then 
				pnode.potentialnode = New potentialnode
				pnode\x = node\x
				pnode\y = node\y
				pnode\g = 14
				node\open = False
			EndIf	
		Next
		;determine h, f (g was found above), and lf(lowest f)
		For pnode.potentialnode = Each potentialnode
			pnode\h = 10 * (Abs(currentx - goalx) + Abs(currenty - goaly))
			If pnode\h + pnode\g < lf Then 
				lf = pnode\h + pnode\g
				pnode\lf = True
			EndIf
			n = n + 1
		Next
		Text 0, 20, n
		n=0
		;delete all potentialnodes, open up the closed nodes, and set currentx and y to the location of the lowest f
		For node.goodnode = Each goodnode
			If ((node\x = currentx - (gridscale*100)) And (node\y = currenty)) Or ((node\x = currentx) + (gridscale*100) And (node\y = currenty)) Or ((node\y = currenty - (gridscale*100)) And (node\x = currentx)) Or ((node\y = currenty + (gridscale*100)) And (node\x = currentx)) Then node\open = True 
		Next 
		For pnode.potentialnode = Each potentialnode
			
			If pnode\lf = True Then
				currentx = pnode\x
				currenty = pnode\y
				lf = 10000000
				hnode.hlnode = New hlnode
				hnode\x = pnode\x
				hnode\y = pnode\y
			EndIf
			Delete pnode
			
		Next
		 
		
	Until currentx = goalx And currenty = goaly Or KeyHit(1)
End Function 

**EDIT**updated the code