Okay, so let's forget all the irrelevant stuff about multi-selection, another form etc.
It seems that your actual requirement is creating a form that shows data across companies and you can filter by a particular company or companies. The data source is your custom table, ISPEmployeeInformations, which (I'm assuming) stores data per company. Please confirm.
According to your code, you want the query to be cross-company in all cases (because you call allowCrossCompany() without any condition), therefore the best approach is not doing it in code at all. Instead, set Cross Company Auto Query property of the data source to Yes.
You forgot to tell us where the error was thrown, but anyway, I can already point to to several bugs you can in the meantime.
First of all, let's throw away unrelated code and simply the remaiming:
public class EmployeeInfoActiveWithDetailsConsolidated extends FormRun
{
public void init()
{
ISPEmployeeInformations_ds.queryBuildDataSource().addCompanyRange("USMF, USRT");
super();
}
[DataSource]
class ISPEmployeeInformations
{
public void init()
{
super();
this.queryBuildDataSource().addRange(fieldnum(ISPEmployeeInformations, DataAreaId))
.value(queryValue("USMF, USRT"));
}
}
}
You followed Mohamed's suggestion to use addCompanyRange(), but you forgot to remove the range causing the error.
Another problem is that you call addCompanyRange() above super(), i.e. before the form was initialized.
One more bug I see that the value passed to addCompanyRange() is wrong. It should be a company ID, not a string with multiple company IDs delimited with comma. To filter by multiple companies, call addCompanyRange() several times, each time with a single company ID.