Вы имеете в виду что-то подобное:
<string name="week0">Poam 0</string>
<string name="week1">Poam 1</string>
<string name="week2">Poam 2</string>
int weekOfYear = new GregorianCalendar().get(Calendar.WEEK_OF_YEAR);
String poamOfWeek = getString(getResources().getIdentifier("week" + String.valueOf(weekOfYear), "string", getPackageName()));