private void setFields() {
		String name = block.getName();

		blockOneNameField.setText(name);
		blockOneNameField.setEnabled(false);

		Address startAddr = block.getStart();
		Address endAddr = block.getEnd();

		blockOneStartField.setText(startAddr.toString());
		blockOneStartField.setEnabled(false);

		blockOneEnd.setAddress(endAddr);
		blockOneEnd.setAddressSpaceEditable(false);

		blockOneLengthField.setValue(Long.valueOf(block.getSize()));

		blockTwoNameField.setText(name + ".split");

		blockTwoStart.setAddress(startAddr);
		blockTwoStart.setAddressSpaceEditable(false);

		blockTwoEndField.setText(endAddr.toString());
		blockTwoEndField.setEnabled(false);
	}
Set the fields according to the block that is to be split.
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/memory/SplitBlockDialog.java