Used JewishGen Gazetteer to locate four Valki in Ukraine. URL does not hold.
Argin, Balki, Valki, Balky populated place
45°00' N 34°27' E Ukraine
417.6 miles SSE of Kyyiv 50°26' N 30°31' E
Valki, Valky populated place
49°50' N 35°37' E Ukraine
229.4 miles E of Kyyiv 50°26' N 30°31' E
Valki, Volki populated place
50°38' N 32°31' E Ukraine
88.9 miles E of Kyyiv 50°26' N 30°31' E
Valki populated place
50°18' N 37°19' E Ukraine
299.4 miles E of Kyyiv 50°26' N 30°31' E
Closest to Kyiv,89 miles due E, is Valki > Prylutskij district > Chernihiv oblast/region.
There is a Valki (called Walky by Germans), 230 miles DUE E of Kyiv, which is a district center seat, w/appx population 40,000 in Kharkiv oblast. Also village Valki, located 300 miles E of Kyiv, in Kharkiv oblast. THERE ARE HONCZAR LIVING IN VALKY > KHARKIV OBLAST TODAY.
Other too far away on Crimean Penninsula.
Could Viktor have been using Kyiv as a geographic reference point? I see by your nick that you might be in Australia. If so, have you documented Viktor thru Australia Archives and thru Bad Arolsen Archives in Germany?
Migrant Selection Records for WW2 DP (Displaced People) are invaluable: http://www.naa.gov.au/collection/explore/migration/
Contact the Bad Arolsen Archives. There are appx 5 miles of shelves, stuffed w/DP records, being digitized. These archives will provide you w/details of Viktor's exact experience in German territory and other personal details like EXACT place of origin. Inquiry by immediate family is available for free. All you need to provide full name of person and any other spelling variants and exact birth date. Do not provide more info than that. You want the archivists to locate any and all records possible. Additionally, you can make an inquire for more than one person at a time.
Your inquiry can be done by e-mail. Response can take as little as three days or as much as six months.
Upon accessing site click FAMILY REQUESTS on top. Follow instructions.http://www.its-arolsen.org/en/homepage/index.html
Matwij = equivalent to Mathew in English