bool GlobalVariableSetOnCondition	(	string	name,
		double	value,
		double	check_value
	)

Sets the new value of the existing global variable if the current value equals to the third parameter check_value.
If there is no global variable, the function will generate an error ERR_GLOBALVARIABLE_NOT_FOUND (4501) and return false.

Parameters

name	Global variable name
value	New value
check_value	The value to check the current value of the global variable

Returns

If successful, the function returns true, otherwise it returns false. For details about the error call GetLastError().
If the current value of the global variable is different from check_value, the function returns false

Function provides atomic access to the global variable, so it can be used for providing of a mutex at interaction
of several Expert Advisors working simultaneously within one client terminal