asp.net Logic to check if user already exist - sql

Question

I have this code to check if a user already exists, but it is not working.
For some reason system is skipping this function:
if Cadastrar_CodEmpresa = verificar("Usuario") Then
Response.Redirect("index.asp?pagina=login")
Here is the code:
if request.Form("commentForm") = "sim" Then
set verificar = conexao.execute ("select * from empresas")
Cadastrar_CodEmpresa = request.Form("CodEmpresa")
Cadastrar_Segmento = request.Form("Segmento")
Cadastrar_Endereco = request.Form("Endereco")
Cadastrar_Bairro = request.Form("Bairro")
Cadastrar_Cidade = request.Form("Cidade")
Cadastrar_CEP = request.Form("CEP")
Cadastrar_Pais = request.Form("Pais")
Cadastrar_Contato = request.Form("Contato")
Cadastrar_Telefone = request.Form("Telefone")
Cadastrar_Email = request.Form("email")
if Cadastrar_CodEmpresa = verificar("Usuario") Then
response.Redirect("index.asp?pagina=login")
Else
set cadastrar_cadastro = conexao.execute("insert into Empresas (Usuario) Values ('" & Cadastrar_CodEmpresa & "')")
End if
... some more stuff ...
End if