Bug 4240 Can't edit class path entry (1GKEPIF)
There is no way to edit an existing entry for a library on the Java Build Path project properties page (other than editing the .classpath file directly). NOTES: EG (9/22/2001 11:42:11 AM) this is particularly annoying for variables. we should have an Edit button when a variable is selected.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/wizards/buildpaths/NewContainerDialog.java
public void setMessage(String message) {
		fContainerDialogField.setLabelText(message);
	}
	
		
	protected Control createDialogArea(Composite parent) {
		Composite composite= (Composite)super.createDialogArea(parent);
		
		int widthHint= convertWidthInCharsToPixels(80);
		
		Composite inner= new Composite(composite, SWT.NONE);
		GridLayout layout= new GridLayout();
		layout.marginHeight= 0;
		layout.marginWidth= 0;
		layout.numColumns= 1;
		inner.setLayout(layout);
		
		fContainerDialogField.doFillIntoGrid(inner, 2);
		
		LayoutUtil.setWidthHint(fContainerDialogField.getLabelControl(null), widthHint);
		LayoutUtil.setWidthHint(fContainerDialogField.getTextControl(null), widthHint);
		LayoutUtil.setHorizontalGrabbing(fContainerDialogField.getTextControl(null));
				
		fContainerDialogField.postSetFocusOnDialogField(parent.getDisplay());
		return composite;
	}
		
	
	private class SourceContainerAdapter implements IDialogFieldListener {