Adding tab stop to index

I am trying to create a nomenclature page for my master's thesis using an
index. I essentially want three columns in the nomenclature - the
abbreviated term, the expanded version, and the page number of the first
instance used. I would like the abbreviated terms to be aligned at 0 on the
ruler; the expanded version to be left aligned beginning at 1.5"; the page
numbers to be right aligned at 6.5".

Getting the page numbers aligned is not an issue. My problem is
establishing the second column. Below is the default marked entry text
within the field code:
DOF{ XE "DOF: degree of freedom" }

I can go into each entry and delete the colon and insert a tab, but I cannot
get it to display correctly when I update the index. The tab appears in the
index simply as a space. Two tabs = two spaces. Imagine the "-" equals the
tab arrow.
DOF { XE "DOF - degree of freedom" }


I have also tried the following:
Right-click on the index -- Edit field -- Index -- Modify (using the "From
template" as my format) -- Modify (with Index 1 highlighted) -- Format -- Tabs

The tabs dialog box already had 6.49" entered as a tab stop position. I
added 1.5", chose left aligned, with no leader, clicked Set and then OK.

This still doesn't allow my inserted tab within the field code to appear as
a tab in the Index - it leaves it as a space. After updating the index I can
manually format it to my desired look but as soon as I update the table again
to refresh the page numbers it goes back to the default formats. Any
thoughts?