No, the field must be entered if you are calculating holds based on R&T number.  However, remember that the system will allow you override the number of days to place a hold, and you can even set that to 0 days if you want.  (Whenever you enter something manually into the Days field, that always takes precedence over any calculated amount.)  So you would enter the R&T #, the check amount, 0 days, and the account type (you still need a valid suffix even though the won't really be adding a hold record) to bypass the calculation.