Please see line below:
if (doc.Range.FormFields[j].Type == Aspose.Words.FieldType.FieldFormCheckBox)
C:\AppSoft\Visual Studio Projects\FileTrax\Modules\Merge\Merges.cs(447,42): error CS0234: The type or namespace name 'FieldType' does not exist in the class or namespace 'Aspose.Words' (are you missing an assembly reference?)