I need to find the highest value of all tags named DataAge under a Context Tag PC regardless of context depth.

Should be easy enough to script.
something like:
DataAges = \GetTagList(scope(\VTSDB, "PC"\Name, TRUE, 0, "DataAge", Invalid, Invalid, False);

then use something like
Whileloop(i < arraysize(DataAges),
{if Highest dataage < dataAges[i] then Highest dataage = dataAges[i] }
{i++}

Hope this helps....