blank value vs zero

Hi Experts,

I'm doing coding in transformation rules and requirement is as below:-

The field is currency amount field

so if the field is blank ---need to write nothing in field a and keep it as blank

or if field is having value then--- need to calculate mod of this amount field

amount field mod 1000 .

If the results are zero then need to write xyz in field a.

If the results are non zero then need to write jhk in field a.

The problem is abap code is assuming blank value as 0 value , so for abap 0 or ' ' or is initial is same.

I can't distinguish between these three in codes every time its coming xyz.

Pls help.

Thanks