Mod_rewrite - Catching URL Paramaters Then Matching Them Using RewriteMap

My current URLs look like index.php?order=key, where 'key' is of course the key. I'd like to transform my URLs to a pattern that doesn't currently have any association with the 'key' used in the URL. I'm using the RewriteMap directive to map keys to new values. If I can take the following example URL:-

I'd like to transform index.php?order=hc to /homecare, so I've mapped the key with the value in the two column syntax required within a text file and linked to it.

My initial assumption was that I could then just RewriteRule the variable, but from what I've read I need to use RewriteCond to capture the query_string first.

So, this is my complete ruleset so far:-

RewriteEngine on
RewriteMap rewritemap txt:C:/WINDOWS/system32/inetsrv/rewrite/rewritemap.txt
RewriteCond %{QUERY_STRING}
RewriteRule ^(.*) test.asp?order=${rewritemap:$1}
I'm pretty sure my RewriteRule is correct, but of course there is no rule currently attached to RewriteCond, since I'm unsure what I need to put there.

Would you guys be kind enough to help me out a bit?