Count Logic

Hi,

i have a rquirement here,

in a start routine, we are reading an internal table after checking one condition i.e. field 1 and field 2 are not initial.

if we get any records,what we are doing is we are populating some fields through another table.

now my requirement is:

-if field1 and field2 are not blank then check for no. of such records.

-if count is only 1 then populate the other fields as usual

-else other condition.

can anyone plese tell me , how can i be able to implement this logic (count logic)??