how to sort lines with a $ amount

[larry at significantplanet.org]

I have a field with a date, name, number and finally a dollar amount such as $10 - in each line of the field.

I can sort the lines of the field just fine on word 1 (date),  word 2 (name) and word 3 (number)

But when I try to sort on word 4, I don't know how to get it to come out right because the $ in front makes it a string and not a number.

So I get something like this:
$11.00
$120.00
$47.00

When what I want is:
$11.00
$47.00
$120.00

Thanks in advance for any enlightenment!
Larry