diff --git a/RhSolutions.AddIn/Tools/WorksheetExtensions.cs b/RhSolutions.AddIn/Tools/WorksheetExtensions.cs
index 0d4f9f3..29ab798 100644
--- a/RhSolutions.AddIn/Tools/WorksheetExtensions.cs
+++ b/RhSolutions.AddIn/Tools/WorksheetExtensions.cs
@@ -1,8 +1,5 @@
 #if !NET472
 using System.Runtime.Versioning;
-using RhSolutions;
-using RhSolutions.Services;
-using RhSolutions.Tools;
 #endif
 
 namespace RhSolutions.Tools;
@@ -12,6 +9,9 @@ namespace RhSolutions.Tools;
 #endif
 public static class WorksheetExtensions
 {
+    private static readonly Dictionary<string, string> pricelistParameters =
+        RhSolutionsAddIn.Configuration.GetPriceListHeaders();
+
     public static bool IsValidSource(this Worksheet worksheet)
     {
         Range amountCell;
@@ -19,8 +19,6 @@ public static class WorksheetExtensions
         Range programLineCell;
         Range nameCell;
 
-        var pricelistParameters = RhSolutionsAddIn.Configuration.GetPriceListHeaders();
-
         Range[] cells = new[]
         {
             amountCell = worksheet.Cells.Find(pricelistParameters["Amount"]),