Sort custom fields

Hello,

I have digged the hole day long for being able to sort custom fields with only the help of the query_posts() attribute.

I find it hard to implement the technique described here: http://ww.wp.xz.cn/support/topic/sort-posts-by-custom-field-numeric-value?replies=12

My “problem” is that I have both numbers and letters in the custom_fields like the following example:

meta_key meta_value
cow_type belgienblue
cow_legs 40
cow_nose 1
cow_type Awsome-Cow
cow_legs 7
cow_nose 2

I want to be able to sort by all the meta keys (cow_type, cow_legs, cow_nose). With all I mean not all at the same time, but when I click a link for cow_type, cow_type should be ordered and cow_legs and cow_nose is then independent. As you can se when sorting cow_legs, it is a number and when sorting on cow_type it is letters.

So here I’m stuck using the technique http://ww.wp.xz.cn/support/topic/sort-posts-by-custom-field-numeric-value?replies=12

Because then the SQL-question should look different depending if it is a letter or number based custom_fields.

So my question is, do I have any chance to solwe this with a query_posts() statement or is this impossible and I most use the technique linked above?