Hello Hari,
The content area will never grow if the number of items gets increased. It is the sub form which grows if the number of items get increased. So declare the content area with the static size you want(say 90 mm i.e 10 mm above footer). And let the table sub form flow as usual.
Now the trick here is that the horizontal bottom border should be given at the content area level and not at the sub form level. This will ensure that the table height is always 90 mm i.e 10 mm above footer. And you can provide the Horizontal top border either at sub form level or content area level. It doesn't matter. And if you are providing vertical lines for columns, draw the lines from top to bottom of content area in Master Page. Problem solved.