How about:

CALCULATE SUM (R1), SUM (R2), ... TO ARRAY aColSums
lnTotal = 0
FOR X = 1 TO ALEN (aColSums, 1)
    lnTotal = aColSums [X] + lnTotal
ENDFOR

With 30 fields, you may run into a limit issue, but this can be resolved by breaking into multiple runs.

Jay