[AccessD] add numbers

Hello Group,

i have a table with a field [Para], that has values like:

2(2ma)
3(0v)
2(2v+2a)

what i would like is the total of numbers of field [Para],
as result in a new field [Para_total].

the result would be

4                  2(2ma)    = 2+2
3                  3(0v)        = 3+0
6                  2(2v+2a) = 2+2+2

Thanks 

Pedro Janssen