Custom Header in a crosstab

[Phil Scottow]

Report Studio V10.1
I am trying to make a columns header in a crosstab dynamic.
So far. If I click on the column header and change text source > source Type from 'Member Caption' to 'Report expression' and do a simple Report Expression Today() all works well.
but when I try to extend this Report expression to _first_of_month (Today ())
I just get a CRX-API-0014
An invalid function argument type was found at or near the position '24' in the expression "_first_of_month (Today ()) ".

there must be a simple way around this. Can anyone advise me
Thanks

[Phil Scottow]

Well this is what I came up with. and it works. change the add months value as required.

case substring(timestamp2string (_add_months (_first_of_month (date2timestamp (Today ())),-12)),6,2)
when '01' then 'JAN'
when '02' then 'FEB'
when '03' then 'MAR'
when '04' then 'APR'
when '05' then 'MAY'
when '06' then 'JUN'
when '07' then 'JUL'
when '08' then 'AUG'
when '09' then 'SEP'
when '10' then 'OCT'
when '11' then 'NOV'
when '12' then 'DEC'
end
+' '+substring (timestamp2string (_add_months (_first_of_month (date2timestamp (Today ())),-12)),1,4)