Here is my stab at is:

test.kix
code:
$KEY = "HKLM\Software\CLASSES\exefile\shell\open\command"
$LINE = CHR(34) + "%1" + CHR(34) + " %*"
$READ=READVALUE($KEY,"")
IF $READ <> $LINE
WRITEVALUE($KEY,"",$LINE,"REG_SZ")
ENDIF

Brian