It sounds to be of Bielorussian origin. It is quite possible to find such a name on the other side of the border as most locals in the vicinity of Białowieża didn't move accordingly to the change of frontiers after the WWII.
I had a look on moikrewni and there is only the one £okucewicz on there! in Olsztyn. However on nasza-klasa there is a Barbara Osik nee £okucewicz living in Olsztyn, 66 year old. If you sign up you can message her. Thats a pretty good start i think:) Also try kresy5.webpark.pl/strony-o-kresach.html
ekonomik.olsztyn.pl/?q=search/node/%C5%81okucewicz there are 2 graduates listed in this Olsztyn school
Hi thank you for your trouble. I had seen those names previously. Barbara is the one registered at the school. Somebody has written to her on my behalf at nasza-klasa but still not reply. If Lokucewicz is such a regular name why can I only find one lady who is now married?
dear muffin, there are two sisters playing for AZS Olsztyn vollebay team named £okucewicz, I don't know however if they are Polish or perhaps Belarusian
oh, I have mislead you here- I am sorry- I thought the excerpt I found was current news - now that I actually read the page it is obvious it was not - this is archival news of 1964 - and two women of the surname were mentioned - Barbara (who probably is the same person as on Nasza Klasa, ) and Regina. No further details there.
the surname is regular Polish not in the sense that it is widely used - I told you it is rather improbable your granddad changed the name because the one you bear after him fits Polish perfectly (but also Belarusian) - this is what I meant saying it is a regular Polish name