Do as following
1. Make CompanyName field a LinkButton, add a OnClick event and set CompanyId as CommandArgument.
2. Add another GridView say gvCompanies
3. On the click of the LinkButton following code will be executed
Protected Sub lnkCompany_Click(sender As Object, e As EventArgs)
Dim companyId As String = TryCast(sender, LinkButton).CommandArgument
'Make database call here and bind gridview gvCompanies
End Sub