Validating lambda expression parameter in mocked method

I'm fairly new to TypeMock and have found it pretty easy to get going but have gotten stuck.

I'm trying to write tests for derived service objects that use lambda expressions. I want to verify the method is called with a specific lambda expression and returns the value.

I can't figure out how to test that a specific lambda expression is used:
item => item.Name == "MyBusinessUnit"

Any ideas?

Test:

[TestMethod]
[VerifyMocks]
public void Test()
{
    BusinessUnit myBusinessUnit = new BusinessUnit{Name="MyBusiness"};
    BusinessUnitService businessUnitService = new BusinessUnitService();
    Isolate.WhenCalled(() => businessUnitService.GetObject(null)).WillReturn(myBusinessUnit);

    businessUnitService.GetBusinessUnitByName("MyBusiness");

    Isolate.Verify.WasCalledWithExactArguments(() => businessUnitService.GetObject(item => item.Name == "MyBusinessUnit"));
}

The method under test:

public BusinessUnit GetBusinessUnitByName(string businessUnitName)
{
    return GetObject(item => item.Name == businessUnitName);
}