Ha...that is funny. It actually worked and I didn't even know it because I thought I would need to use some different login mechanism. Sorry, my brain was going in a completely different direction. Thanks for the help.
For anyone else trying to do the same, below are the changes I made to the
Under <system.web>, change:
<authentication mode="Forms" />
<authentication mode="Windows" />
Under <connectionStrings>, add:
<add name="ADConnectionString" connectionString="LDAP://dc.somecompany.com:389/DC=somecompany,DC=com" />
Under <providers>, add:
<add name="MyADMembershipProvider" type="System.Web.Security.ActiveDirectoryMembershipProvider, System.Web, Version=22.214.171.124, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" connectionStringName="ADConnectionString"
connectionUsername="domain\someuser" attributeMapUsername="SAMAccountName" connectionPassword="myPassword" connectionProtection="None"/>