"Application uses a value of the wrong type" Error

Why are you using nvarchar in your stored proc?
Shouldn't you be using varchar?

hclgroup,

That part of the code works perfectly. As I stated above, the email part of the code works fine. The problem exists only when I leave the "respondentid" field blank. If I were to comment out this line, adocmd.Parameters("@Respondentid") = Request.Form("respondentid") and run the program by entering some data in the email field, the program executes.
The program also executes when I have data in the 'respondentid' field. The problem only persists when the 'respondentid' is left empty.
Thanks for your help.

Doh! I thought I had tried that. Alright well I created this if-then statement:
      if (Request.Form("respondentid") = "") then
            adocmd.Parameters.Append adocmd.CreateParameter("@Email",adVarChar, adParamInput, 75)
            adocmd.Parameters("@Email") = Request.Form("email")
            set objRS = adocmd.Execute
      else
            adocmd.Parameters.Append adocmd.CreateParameter("@Email",adVarChar, adParamInput, 75)
            adocmd.Parameters.Append adocmd.CreateParameter("@Respondentid",adDecimal, adParamInput, 19)
            adocmd.Parameters("@Respondentid").Precision = 19
            adocmd.Parameters("@Respondentid").NumericScale = 0
            adocmd.Parameters("@Email") = Request.Form("email")
            adocmd.Parameters("@Respondentid") = Request.Form("respondentid")
            set objRS = adocmd.Execute
      end if

It appears to be working fine at a certain extent. The problem I am having now is that if I were to enter both of the fields (Email and respondentid), it will not check to see if the email is in the correct email format (which it will do if ONLY the email field was filled out). Also, if both fields were filled out and the respondentid was the correct one but the email was incorrect, it will still show the results because the respondentid was filled out correctly thus returning the results.
I would like it so if both fields are filled out and if one of the fields are incorrect (as in that it won't match the database table), the output will show 'no results found'.
Am I making sense or not? Let me know if you got some suggestions. Thanks

Alright I figured out what I was doing wrong BUT I have another question if you can assist me on it.
As you know I have two fields (Email and RespondentID). The user has the option of choosing either or but never both of them.
Is there a javascript code which will disable one field if the user decides to type in another field.
Ex: The user types in an E-mail, the RespondentID field box will be disabled in that the user will be Unable to type in anything in there; and vice versa.

I have found codes which disable and enable but not what I am looking for as stated above.
Any Help wil be appreciated. Thanks

Nevermind I fugured it all.