How to lock Field Size

[Henry]

Hi there, i found that every time i create a field on a layout and then type some word in the field, if i keep on type enter, the field will become enlarge. Can i fix or lock the size of the field so that they only can entry in a fixed size field, just like if i set the field with two line, then they only can type on this two line, even type enter still cannot jump into the other line. I know i can set the max number of the charactor, i found that that one still not very good enough to fix this problem, so is there got any way to solve the problem.

Regards

Henry