This is related to the "Node availability (percentage)" DCI only (other DCIs are OK):
See attached Capture1.PNG

Here's the error msg:
See attached Capture3.PNG

Here's the line of code being referred to:
See attached Capture2.PNG

Here's the full script:

// This script calculates MTTR, MTBF and perAvailability parameters and stores them in custom attributes
// Initialize some custom attributes the first time.
// Undefined attributes are created by SetCustomAttribute function automatically
CurrentStatus = GetDCIValue($node, FindDCIByName($node, "Status"));
PreviousState = GetCustomAttribute($node, "PreviousState");
if (PreviousState == null)
{ // In the first time, previous state is null
	SetCustomAttribute($node, "PreviousState", CurrentStatus);
	SetCustomAttribute($node, "TimeStamp", time());
	SetCustomAttribute($node, "NumFailures", 0);
	SetCustomAttribute($node, "TotalUptime", 0);
	SetCustomAttribute($node, "TotalDowntime", 0);
	return 100;
}

// From here the 2nd and subsequent times
NumFailures = GetCustomAttribute($node, "NumFailures");
LastTime = time() - GetCustomAttribute($node, "TimeStamp");

// Status is up
if (CurrentStatus == 0)
{
	if (PreviousState != CurrentStatus)
	{   // just changed to up
		// update mttr
		TotalDowntime = GetCustomAttribute($node, "TotalDowntime") + LastTime;
		mttr = TotalDowntime / ((NumFailures == 0) ? 1 : NumFailures) / 3600;   // to prevent division by ze
		SetCustomAttribute($node, "TotalDowntime", TotalDowntime);
		SetCustomAttribute($node, "mttr", mttr);
	}
	else
	{      // still up
		// update mtbf
		TotalUptime = GetCustomAttribute($node, "TotalUptime") + LastTime;
		mtbf = TotalUptime / ((NumFailures == 0) ? 1 : NumFailures) / 3600;   // to prevent division by zero
		SetCustomAttribute($node, "TotalUptime", TotalUptime);
		SetCustomAttribute($node, "mtbf", mtbf);
	}
}

// Status is down
if (CurrentStatus == 4)
{
	if (PreviousState != CurrentStatus)
	{   // just changed to down
		// update mtbf
		NumFailures++;
		TotalUptime = GetCustomAttribute($node, "TotalUptime") + LastTime;
		mtbf = TotalUptime / NumFailures / 3600;
		SetCustomAttribute($node, "NumFailures", NumFailures);
		SetCustomAttribute($node, "TotalUptime", TotalUptime);
		SetCustomAttribute($node, "mtbf", mtbf);
	}
	else
	{   // still down
		// update mttr
		TotalDowntime = GetCustomAttribute($node, "TotalDowntime") + LastTime;
		mttr = TotalDowntime / NumFailures / 3600;
		SetCustomAttribute($node, "TotalDowntime", TotalDowntime);
		SetCustomAttribute($node, "mttr", mttr);
	}
}

if (CurrentStatus == 0 || CurrentStatus == 4)
{
	// Save previous state and timestamp
	SetCustomAttribute($node, "PreviousState", CurrentStatus);
	SetCustomAttribute($node, "TimeStamp", time());

	// perAvailability section
	TotalUptime = GetCustomAttribute($node, "TotalUptime");
	TotalDowntime = GetCustomAttribute($node, "TotalDowntime");
	perAvailability = TotalUptime / (TotalUptime + TotalDowntime) * 100;
	SetCustomAttribute($node, "perAvailability", perAvailability);

	return perAvailability;
}

Appreciate any help.
Thanks