@Override
    void setEndAddress(Address addr) {
		message="";
		endAddr = addr;
		
		if (endAddr == null) {
			message = "Invalid Address";
		}
		else if (block.getEnd().compareTo(endAddr) >= 0) {
			message = "End must be greater than " +
							block.getEnd();
		}
		else {
			length = endAddr.subtract(block.getStart()) +1;	
		}
		listener.stateChanged(null);
	}
@see ghidra.app.plugin.core.memory.ExpandBlockModel#setStartAddress(ghidra.program.model.address.Address)
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/memory/ExpandBlockDownModel.java