VS 2010 Datatable expression COUNTIF or equivalent

Hi there..

In Excel it's possible to do a COUNTIF function on a column... eg say I had a named range called REF filled with

A
A
A
A
B
A
B

formula would be =COUNTIF(REF,"A")

In my datatable I have a load of numbers in a column called REF

111
222
222
333
333
333

I want to be able to calculate in the end column on each ROW the count of column REF if the column = what's currently in REF

so the count would show

1
2
2
3
3
3

Can this be done using basic expressions?