Using Variables In SQL Statement

I am trying to use two variables in my SQL statement to query an access database and then pass the results to a datagrid. Nothing shows up in my datagrid. I think that the syntax on my SQL statement is wrong. I am really not sure how to embed the variables, especially since there are two. I really need help with this, it is for work. The code is posted below. Thanks.

Sub Search_Click( s as Object, e as eventArgs)

Dim conLibrary As OleDbConnection
Dim Category As String
Dim Search_Field As String
Dim dstResults As DataSet
Dim dadResults As OledbDataAdapter
Dim dtblBooks As DataTable


conLibrary = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0; Data Source=D:
ewpsychiatrylibrarydb.mdb")
conLibrary.Open

Category = ddlSearch.SelectedItem.text
Search_Field = txtSearch.text
dadResults = New OledbDataAdapter("Select * From rec WHERE '"& Category"' "="  '"&Search_Field"'", conLibrary)

dstResults = New Dataset()
dadResults.Fill(dstResults, "Table1")

dgrdResult.DataSource = dstResults.Tables(0).DefaultView

dgrdResult.DataBind()

conLibrary.close
Server.Transfer("results.aspx")

end Sub