I am trying to create an index in a microsoft word 2002 document. I am
trying to create a concordance file to do this but the content of the
concordance file does not mark words in a document when i use the colon
command for a sub entry. For example if i want an entry which reads
'planets' under which 'mars' and 'venus' appears, word will not mark these
words. Does anyone have an example of how the concordance file should look
that i can follow?

Use a two column table:

Col 1 Col 2

planets planets
mars planets:mars
venus planets:venus