Use the formula in update rule

Hi,

I need to load data from text data source that have 2 fields for representing month and year with the format as Jan,2007 Feb,2007 Mar,2006..... I need to transform them to 200701, 200702, 200603 for load them into 0CALMONTH, right?

Can the formula support this transformation? and How?

I tired to use IF( , ,IF ( , , IF( ))) ,but it doesn't allow to do like that.

Please suggest.

And for the future , where can I download the document for the formula using?

Thanks in advance.

Chet