Interpolation

I have an excel sheet for beam design,the sheet is uploaded along this mail.I want to interpolate shear strength of of concrete for percentage of steel that is given in cell B25.The grade of concrete is dependent on cell B8 which means as I change the value of cell B8,accordingly the interpolation column should also change.Column P represents percentage of steel whereas columns Q to V represents different grade of concrete. The interpolated answer should be entered in cell B26.
Please help me do this and please give me step by step input.
If you are not able to find the file please mail me on [email protected] and I'll mail you the sheet.
Thank you.

I think you were virtually there.

Change P21 to

=MATCH(B4,Q2:V2,0)

and P23 to

=INDEX(percentsteel,P20+1)

Does that work. Btw, I think P7 should be 1, not 0.1.

QUOTE=StephenR;2361499

Thank you STEPHENR I was waiting for sum1 reply.I think i'll need your help more often since I work extensively on excel and I always get stuck while working with it.I am trying to make small programs using excel as I am a structural consultant.
So I think i'll be disturbing you a lot the next time I get stuck.
Thank you once again.
Hope to get your reply.
Waiting.