diff --git a/PROMS/Volian.Controls.Library/DisplaySearch.cs b/PROMS/Volian.Controls.Library/DisplaySearch.cs
index 447b6de9..38de36b7 100644
--- a/PROMS/Volian.Controls.Library/DisplaySearch.cs
+++ b/PROMS/Volian.Controls.Library/DisplaySearch.cs
@@ -2058,7 +2058,10 @@ namespace Volian.Controls.Library
 				}
 			}
 			buildStepTypePannelTitle();
-
+			// B2021-100: Enable/disable the RNO Only checkbox & WORD Sections tree node in Step Elements to Search.
+			//	The only time the RNO Only checkbox is disabled is if the only selection in Step Elements to Search is WORD Sections.
+			cbxRnoOnly.Enabled = true;
+			if (OnlyWordSectTypeSel()) cbxRnoOnly.Checked = cbxRnoOnly.Enabled = false;
 		}
 
 		private void xpStepTypes_ExpandedChanged(object sender, ExpandedChangeEventArgs e)
@@ -2167,11 +2170,30 @@ namespace Volian.Controls.Library
 				Clipboard.SetDataObject(myDO);
 			}
 		}
+		private bool OnlyWordSectTypeSel()
+		{
+			// B2021-100: Enable/disable the RNO Only checkbox & WORD Sections tree node in Step Elements to Search.
+			//	lstCheckedStepTypes[x] = 0 for Word sections:
+			if (lstCheckedStepTypes != null && lstCheckedStepTypes.Count == 1 && lstCheckedStepTypes[0] == 0) return true;
+			return false;
+		}
 		private void CbxRnoOnly_Click(object sender, System.EventArgs e)
 		{
 			// C2021-028: RNO Only search, disable Word section tree node: 
-			wordSectionTreeNode.Enabled = !(tabSearchTypes.SelectedTab == tabTranSearch || !cbxRnoOnly.Checked);
-			if (!wordSectionTreeNode.Enabled) wordSectionTreeNode.Checked = false;
+			// B2021 - 100: Enable / disable the RNO Only checkbox &WORD Sections tree node in Step Elements to Search.
+			if (tabSearchTypes.SelectedTab == tabTranSearch) return;
+
+			wordSectionTreeNode.Enabled = true;
+			if (!cbxRnoOnly.Checked)    // checked turning on
+			{
+				// Set enabling on WORD Sections tree node in Step Elements to Search. If either no items are selected in tree or
+				//	just WORD Section is selected, then disable the WORD Section tree node.  Otherwise, i.e. other step types are selected
+				//	in tree, thus they must be searched using RNO Only so need to disable anything.
+				wordSectionTreeNode.Enabled = !(OnlyWordSectTypeSel() || (lstCheckedStepTypes != null && lstCheckedStepTypes.Count == 0));
+				if (!wordSectionTreeNode.Enabled) wordSectionTreeNode.Checked = false;
+			}
+			else  // turning off - WORD Sections tree node is enabled.
+				wordSectionTreeNode.Enabled = true;
 		}
 		private void cmFndTxtPaste_Click(object sender, EventArgs e)
 		{