Thanks Gang, Daniel for your quick response

er.. yes, i meant 3dTstat rather than 3dTcalc.

Yes, I had thought of using inline sub-brick selectors, but for the case where i'm trying to do a block design, this seems rather cumbersome.

3dcalc seems to be able to operate with 1D files, but unless i'm missing something, i don't seem to be able to "select" using a 1D file.

e.g. if a voxel time series is
1 2 3 4 5 60
and i have a censor file
1 1 1 1 1 0, I would want to get an average of (1+2+3+4+5) / 5 = 3 rather than (1 +2+3+4+5+0)/6 = 2.5

Perhaps lack of laziness (ie typing out sub-bricks) is the only solution.