Using Global Variables & ScriptClip

[shakana]

Sample Code
function a(bool isGoodFrame)
{
goodFrame = isGoodFrame ? current_frame: goodFrame
c = Subtitle(String(goodFrame))
}

global goodFrame = 0
source = avisource("testclip.avi")
ScriptClip(source, "a(isGoodFrame)")
ConditionalReader(source, "dataFile.txt", "isGoodFrame", false)

In short, this sample code reads a file indicating if a frame looks good or not. It sets goodFrame to the frame number of the last good frame.

How do I get goodFrame to hold its value across frames. It always gets set back to 0.