Basic Login Mechanism

Hi community,

Im trying to do a simple thing.
I have an excel sheet with membernumbers on.
I want to import this list and use it to validate against.

The "login" screen would then just have an input field for a member to enter his membernumber, then an action needs to check and see if this member number exists in that table. If it exists, it must move to a next screen which will then contain a form. simple.

I come from a php backgorund, so in php terms this is extremely easy, input > passvariable > sql query to validitate and done.

Please may I ask your opinions and leverage your knowledge of this platform.
I am stumped.
I have tried looking at the common login action, but this has been pointless.