To improve performance

Question

I have C# dll and register in my computer successfully. I used that dll in web application and every time when user have to create object and destroy object. The problem is if there is more user to access that assembly.It gets slow.How do I solve.In c# we are using the following code to open
public Microsoft.Office.Interop.Word.ApplicationClass appWord;
appWord.Documents.Open(ref file, ref nullobj, ref nullobj, ref nullobj,
                ref nullobj, ref nullobj, ref nullobj, ref nullobj, ref nullobj, ref nullobj, ref nullobj,
                ref oFalse, ref nullobj, ref nullobj, ref nullobj, ref nullobj);
your help is need full.