create a formula (2 actually, maybe 3) with a shared variable.
the formula is pretty simple:
shared numbervar lineCount := lineCount +1
""//to hide the count.
On every line that is displayed, place the formula.
in the page header you will want a reset
shared numbervar lineCount := 0
probably in section expert, for some or all sections (you know how your report is supposed to work/laid out) you can update the newpage after with something like:
shared numbervar lineCount;
lineCount >= 56
it might need some tinkering, but hopefully it will point you in the right direction.
HTH