Margin formatting question for "mom"

[Steve Ross]

All,
Regarding formatting of margins using "mom"...
Is there a way to change the top and bottom margins after the first page?
I see that the macros "L_MARGIN", "R_MARGIN", "T_MARGIN" and "B_MARGIN" are 
available to set margins before the "START" macro.  Correspondingly, the 
"DOC_LEFT_MARGIN" and "DOC_RIGHT_MARGIN" macros are available to (re)set the 
left and right margins before a subsequent "NEWPAGE".  I expected to find, but 
do not, corresponding macros of "DOC_TOP_MARGIN" and "DOC_BOTTOM_MARGIN".
Given that the last two macros do not exist, what can I do to adjust the top 
and bottom margins before executing "NEWPAGE"?
Thanks,-- Steve Ross