In some situations, instead of this:

dim filter as new PredicateExpression(MetricScorecardFields.ScorecardCode = "someValue")

I'd like to be able to do this:

dim theEntityField as New EntityField("MetricScorecard","ScorecardCode")
dim filter as new PredicateExpression(theEntityField = "someValue")

Can it be done?

Yes, this is how:

static IEntityField2 GetFieldFromStrings(string myEntityName, string myFieldName)
{           
    EntityType myEntityType = (EntityType) Enum.Parse(typeof(EntityType), myEntityName + "Entity");
    IEntityField2 theField = EntityFieldsFactory.CreateEntityFieldsObject(myEntityType)[myFieldName];
    return theField;
}

Usage:

EntityField2 theField = (EntityField2) GetFieldFromStrings("Customers", "Country");

IRelationPredicateBucket filter = new RelationPredicateBucket();
filter.PredicateExpression.Add(theField == "Guatemala");
...

Excellent.