I am new to SQL so please bare with me.
What I am tring to achieve is a SQL query that displays results based on one category in which the rest of the query will display results based on the initial category or group. The initial category is a drop down box. Then from there I created a navigation menu with radial button in which refines the search.
For example this is the drop down selections:

dim unitquery as string
if (unit.text = "ALL Model Years" ) then
unitquery = "[Auto_year] BETWEEN" & chr(39) & "1970" & chr(39) & "AND" & chr(39) & "2005" & chr(39)
else if (unit.text = "Mustang Only" )
unitquery = "[model]= 'Mustang' "
else if (unit.text = "Ranger Only" )
unitquery = "[model]= 'Ranger' "
else if (unit.text = "Ranger Only" )
unitquery = "[model]= 'Explorer' "
End if

strSearch = gen.Text

dbcommand = New SqlDataAdapter( "SELECT model, color, engine, navgtn_sys, timestamp " _
& "FROM tbl_name " _
& "WHERE ( " & unitquery & ") AND model LIKE '%" & Replace(strSearch, "'", "''") & "%'" _
& "OR color LIKE '%" & Replace(strSearch, "'", "''") & "%'" _
& "OR engine LIKE '%" & Replace(strSearch, "'", "''") & "%'" _
& "OR navgtn_sys LIKE '%" & Replace(strSearch, "'", "''") & "%'",bcon )


What happens is the farther the query is refined it displays all models not just Mustang or Ranger. This is an example not the actual data I am seeking.
Any ideas where I can improve on this query string to seperate the queries by model as the search is refined?