The number of "lines" is going to depend on one of two things. You are either going to need to find carriage ejects in the field, and count that, or you are going to arbitrarily pick a line length (that's easy...do a Len() to find the how many characters in the field, then divide by your arbitrary line length and you have the number of lines)
Just for grins, why do you want to know how many lines?