Isometric trajectory or arc to hit target

I need to do a 2D isometric (though not necessarily 45-degree oriented) trajectory calculation for the launching of a projectile to hit a target I click on with the mouse; think throwing a grenade in X-Com.

Distance is always known. The program would need to perform calculations to find the angle and/or power or whichever is easiest - I'd not mind hardcoding or faking either as long as the result is that with gravity taken in account, the arcing projectile hits where I clicked.

I checked out
this
link mentioned in a previous post in the Programming section, but I'm not clear on how exactly these concepts translate into code yet.

The assumption is that the height of the launch would always happen from a constant height (say, 100) and the target would always be on a height of 0.

Here's a simplified version of what I've been pissing around with, sans pages of commented-out experimental nonsense.

Strict
Graphics 800, 600, 0

Const GRAVITY:Float   = 0.01

Global origin_x:Float = 100
Global origin_y:Float = 300
Global mouse_x:Float
Global mouse_y:Float
Global distance:Float
Global angle:Float
Global list:TList = CreateList()


Repeat
	Cls
	If KeyDown(KEY_LEFT)  origin_x:-1
	If KeyDown(KEY_RIGHT) origin_x:+1
	If KeyDown(KEY_UP)    origin_y:-1
	If KeyDown(KEY_DOWN)  origin_y:+1
	mouse_x = MouseX()
	mouse_y = MouseY()
	distance = getDistance( origin_x, origin_y, mouse_x, mouse_y )
	angle = getAngle( origin_x, origin_y, mouse_x, mouse_y )
	If MouseDown(1)
		ListAddLast( list, tObject.Create() )
	EndIf
	'-- Draw the origin --
	SetColor( 255, 255, 255 )
	Plot( origin_x, origin_y )
	'-- Draw and update all particles --
	For Local obj:tObject=EachIn list
		obj.update()
		obj.draw()
	Next
	'-- Draw debug info --
	SetColor( 255, 255, 255 )
	DrawText("Distance from origin to mouse: "+distance, 0, 0)
	DrawText("OriginX: " + origin_x, 0, 10)
	DrawText("OriginY: " + origin_y, 0, 20)
	DrawText("Angle: " + angle + 180, 0, 30)
	Flip
Until KeyHit(KEY_ESCAPE)


Function getAngle( x1:Float, y1:Float, x2:Float, y2:Float)
	Local yDiff:Float  = y2 - y1
	Local xDiff:Float  = x2 - x1
	Local result:Float = ATan2( yDiff, xDiff )
	If result < 0   Then result:+360
	If result > 360 Then result:-360
	Return result
End Function


Function getDistance:Float(x1:Float, y1:Float, x2:Float, y2:Float)
	Local x_diff:Float = x2 - x1
	Local y_diff:Float = y2 - y1
	Return Sqr( x_diff^2 + y_diff^2 )
End Function


'---------------------
'--- Moving object ---
'---------------------
Type tObject
	Field x_start:Float
	Field y_start:Float
	Field x:Float
	Field y:Float
	Field z:Float
	Field x_target:Float
	Field y_target:Float
	Field x_vel:Float
	Field y_vel:Float
	Field dist_target:Float
	Field original_distance:Float
	Field height:Float
	Field rot:Float
	Field time:Int
	Field speed:Float
	Field grav:Float
	
	
	Function Create:tObject()
		Local this:tObject= New tObject
		' -- Velocity & speed vars --
		this.original_distance = distance
		this.dist_target       = distance 'TODO:Recalculate each frame?
		this.rot               = angle    'TODO:Recalculate each frame?
		this.speed             = 2		
		this.grav              = GRAVITY  'TODO:Recalculate each frame?
		this.x_vel             = 0        'TODO:Recalculate each frame?
		this.y_vel             = 0        'TODO:Recalculate each frame?
		this.time              = 0
		this.height            = 100
		'-- Coordinate vars --
		this.x_start           = this.x
		this.y_start           = this.y
		this.x                 = origin_x
		this.y                 = origin_y
		this.z                 = origin_y - this.height		
		this.x_target          = mouse_x
		this.y_target          = mouse_y
		Return this
	End Function
	
	
	Method update()
		If time > 300 Or z >= y 
			killMe()
			Return
		EndIf
		'-- Basic coords --
		x:+speed * Cos(rot)
		y:+speed * Sin(rot)
		z = y - height
		'-- Coord modifiers --
		height:-grav
		grav:+GRAVITY
		time:+1
	End Method
	
	
	Method draw()
		SetColor( 255, 0, 0 )
		Plot(x, y)
		SetColor( 255, 255, 255 )
		Plot(x, z)
	End Method
	
	
	Method killMe()
		list.remove(Self)
	End Method
End Type

If anyone can prod this code in the right direction then true awesomeness is yours forever.

For reference: the red pixel indicates the location of the object on ground level (like a shadow), and white indicates the location of the object at its relevant height.

incase you havent read this yet:

http://blitzbasic.com/Community/posts.php?topic=68027

I have, and posted in it as well. It left me scratching my head.