I have 3 sheets with variable number of rows

Column 5 contains A or B or C or D which is sorted so that all A will
be together and all B will be together etc.

Now is there a way that i can name the range based on the column 5
content?

say i want to name RangeA for the cells haveing A's and RangeB for the
cells haviong B''s etc?

Since the number of rows will be different i want to create dynamic
range names

thanks