afni.nimh.nih.gov

I'm sure this is a basic question but I could not find an easy way to it. We use a combination of 3dToutcount and 1deval to generate a binary censor 1D file. We need to replace the first three values of that censor file with 0s (to censor dummy scans). I've been doing this manually by opening the files and replacing with 0s. I'm sure there must be a simple way to do this in our script to cut out the manual part, but not sure which of the various 1d file tools to use. Any suggestions?