Question-words prefixed with ни- (no stress!) are used with verbs negated by the word не, e.g. Ї никогдђ не љзжу на автћбусе 'I never go by bus'.
Question-words prefixed with нљ- (stressed!) are predicatives, which, like all predicatives, have the meaning 'is'. Thus, just as the predicative Хћлодно means 'It is cold', so Нљкогда means 'There is no time'. And just as the predicative Хћлодно can be expanded by adding a Dative form (Мнљ хћлодно 'I'm cold'), so can the predicative Нљкогда be expanded by adding a Dative form (Мнљ нљкогда 'I have no time').
As with other predicatives, the past is formed with бІло and the future with бџдет.
Here is the rule for the placement of prepositions with these prefixed forms:
Put the preposition between the prefix and the question-word.
Note that the question-word loses its stress when prefixed with нљ-.
Ї ни с кљм не говорќл. I wasn't talking to anybody.
 
Мнљ нљ с кем говорќть. There's nobody for me to talk to.
Мнљ нљ с кем бІло говорќть. There was nobody for me to talk to.
Мнљ нљ с кем бџдет говорќть. There will be nobody for me to talk to.
Мнљ нљгде бІло жќть. I had no place to live.
Нђм нљчего бІло дљлать. There was nothing for us to do.