How do I eliminate duplicate values in cells?
I have a column with the following values:
20
20
30
30
50
60
60
60
90
90
100

How do i eliminate the values that repeat in such a way that the table looks like this:
20

30

50
60

90

100
Namely, how do i make excel only recognize the first value that repeats, and replaces the other duplicate values with a blank cell.
Please help me, and also, what exactly does the "lookup" function do?

have you looked in the help file that you can access from the main program screen .

You're gonna have a problem doing that all in 1 column. You need at least 2 columns, example column A is data entry and column B is data reported.
Try playing around with the =if command.

OK, I found a free minute and fingered out an actual working solution. First the definition of lookup:

Lookup returns a value either from a one-row or one-column range or from an array. The LOOKUP function has two syntax forms: vector and array. The vector form of LOOKUP looks in a one-row or one-column range (known as a vector) for a value and returns a value from the same position in a second one-row or one-column range. The array form of LOOKUP looks in the first row or column of an array for the specified value and returns a value from the same position in the last row or column of the array. This was copied w/o permission directly from the help file.

--A -- B ------------Resulting answer
1
2 20 =if(A2>A1,A2,"") 20
3 20 =if(A3>A2,A3,"") blank cell
4 30 =if(A4>A3,A4,"") 30
5 3= =if(A5>A4,A5,"") blank cell

etc etc etc

I'm not really sure what you were trying to do (a month and a 1/2 ago) but this does return the results you were looking for, as long as the numbers are in a consecutive sequence.

one thing I learned about this you can create a formula in the next row. =if(a2=a1,"yes","") What this will do if the row doubles it will say yes to the doubled word, number, or phrase. Then you will have to manually delete what you have.