Comparing 2 field values using substitution

Hi, I want to check if one CB field is greater then another and display something based on that logic. I have tried the following but cannot get it to work:

[cb:if cb_weightnew < cb_weightold]Well Done[/cb:if]
[cb:if cb_weightnew < "cb_weightold"]Well Done[/cb:if]
[cb:if cb_weightnew < [cb_weightold]]Well Done[/cb:if]
[cb:if cb_weightnew < "[cb_weightold]"]Well Done[/cb:if]

Can this be done? So far I have only seen examples of fields being compared with manually entered strings. Surly there must be a way of comparing 2 CB fields, I just cant work it out.

Any suggestions?...

Many thanks

Make sure that both fields are numeric for the "<" operator to work. If in HTML, you might have to html-specialchar it, e.g.:
[CODE]
< is &lt;
> is &gt;
[CODE]

This excellent tutorial of Kyle might help too:
www.allmysocials.com/directory/tutorials/item/233-substitution-usage