Convert Name of month to a number

I am trying to convert the name of a month to a number but there is a slight issue with using my normal method of TEXT("1/"&A1&"/2013","mmm")

I am trying to create a dynamic table which if you change 1 value for the month, it changes others

so my data looks like so,

Jan
Feb
Mar
Apr
May <---- this is the value which is chosen

the problem is when I select the month "January", it assigns the value of the above cell as 1/0/2013 which is not a date when in fact I want to set it as "December"

im not sure if I am making my problem clear but hopefully someone can understand where my problem lies.

Not quite sure what you mean - can you attach a sample workbook which illustrates the problem better?

Pete

=TEXT("1/"&(IF(P11>12,P11-12,P11))&"/2013","mmm")

this is what I have used....
in P11 i have
=(MONTH(DATEVALUE(README!$B$19&" 1")))+12 <--- this number needs to have +12 because it is referenced in an INDEX.

which is why I have the (P11-12)

Here's a different way of doing it:

=MATCH(P11,{"Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"},0)

Hope this helps.

Pete