I know this post is 2 years old, but I just had the same question and found 1 way to do it, so thought I'd post it here for the next wanderer...
First, set -has_checkboxes which tells the listbuilder that you will create your own checkboxes.
Then, in the -elements section, create an element like this:
-elements {
checkbox {
display_template {<input type="checkbox" name="yourlistkey" value="@yourmultirow.yourlistkey@" @yourmultirow.checkbox@ />}
}
...
}
Then, extend your multirow with the 'checkbox' variable.
db_multirow -extend {checkbox} yourmultirow .... {
if { $my_criteria } {
set checkbox "checked"
} else {
set checkbox ""
}
}
Replace yourmultirow with the name of your multirow.
Replace yourlistkey with the listkey column of your list