Excel help with error bar formula

[akatsafa]

I'm trying to create error bars on excel for a regression problem, but something is not working right. I tried following my instructor's directions, but I think something is wrong with them. Here is the formula I added to the formula bar:
$b$30+$b$31*$a2+sqrt($d$26)

b30 and b31 are my intercept + slope, a2 is my x values, and d26 is the MS residual. I should be getting an error bar above my original line, but instead I'm getting the original line. Can someone please tell me what I'm doing wrong?

Thank you.

 

[rattis]

Is the error so small that it is no showing up against the thinkness of the line?

I usually calculate the percentage error then enter the value in the options of the graph (right click on trendline, i think)