Apply color while exporting to excel if both the CPT code and CPT from first table matches with CPT

//get used range
Excel.Range usedRange= WorkSheet.UsedRange;

//find cell that match your search value
Excel.Range findRange= usedRange.Find(YourSearchValue, missing,
        Excel.XlFindLookIn.xlValues, Excel.XlLookAt.xlPart,
		Excel.XlSearchOrder.xlByRows, Excel.XlSearchDirection.xlNext, false,
        missing, missing); 
		
//mark matches
Excel.Range firstFind = null; 
while(findRange!= null)
{         
	// Keep track of the first range you find.
	if (firstFind == null)
	{            
		firstFind = findRange;
	}         
	// If you didn't move to a new range, you are done.        
	else if (findRange.get_Address(Excel.XlReferenceStyle.xlA1)
				== firstFind.get_Address(Excel.XlReferenceStyle.xlA1))        
	{            
		break;        
	}         
	
	//Apply color        
	findRange.Font.Color = System.Drawing.ColorTranslator.ToOle(System.Drawing.Color.Red);
	findRange.Font.Bold = true;
	findRange = findRange.FindNext(findRange);     
}

using System.Linq;
.
.
DataTable table1 = new DataTable("First");
...//fill you first table with data
DataTable table2 = new DataTable("Second");
...//fill you second table with data
 
//loop thrue the first table rows and collect cpt values
List<string> cptValuesList1 = new List<string>();
foreach (DataRow row in table1.Rows)
{
	cptValuesList1.Add(row["CPTCode"].ToString());
	cptValuesList1.Add(row["CPT"].ToString());
}
//remove doubletts 
cptValuesList1 = cptValuesList1.Distinct().ToList();
 
//loop thrue the second table rows and collect cpt values
List<string> cptValuesList2 = new List<string>();
foreach (DataRow row in table2.Rows)
{	
	cptValuesList2.Add(row["CPT"].ToString());
}
//remove doubletts 
cptValuesList2 = cptValuesList2.Distinct().ToList();
 
//get intersected values 
List<string> intersectList = cptValuesList1.Intersect(cptValuesList2);
.
.
//now use the snippets abow to mark you interesected values