First things first, your API declarations are wrong. They look like they were created for VB6 so, at the very least, you'll have to change all the Longs to Integers. You should look online for declarations that were created for VB.NET in the first place.

Next, you're obviously using late-binding so you should get rid of that for a start. In your project properties you should set Option Strict On and then fix all the errors that result. That will ensure that all your late-binding and implicit conversions are changed to early-binding and explicit conversions. That will most likely highlight where the problem is an force you to fix it at design-time instead of the app failing at run-time.