Dynamic range for a chart

[am003295]

I have a dynamic range set up for a chart and it works good, what I want to do with this now is to make it so the range only selects the last 20 cells from the end of the range.
For example I am selecting out column L starting at row 21 up to a max of 489 rows (I will never get 489 rows filled in so that works for me), I now what to change my start from row 21 to whatever the max is -20, and I can not figure it out.
My dynamic range looks like this:
=OFFSET(Data!$L$21,0,0,COUNTA(Data!$L$21:$L$489))

any suggestions?

 

[wigi]

Not tested, but try:

=OFFSET(Data!$L$21,COUNTA(Data!$L$21:$L$489)-20,20)

 

[am003295]

That had no errors but gave me a blank chart

I was thinking of just replacing the first number 21 in the formula with the countA-20 formula that is there but that gives an error in formula

like:
=OFFSET(Data!$L$COUNTA(Data!$L$21:$L$489)-20,0,0,COUNTA(Data!$L$21:$L$489))

with your suggestion, when I look at the source data for the chart it takes me to cell # AF171 don't know why.

 

[wigi]

=OFFSET(Data!$L$21,COUNTA(Data!$L$21:$L$489)-20,0,20)

 

[am003295]

Perfect !

works great,

can't thank you enought