autofill from a dropdown

hi, i am having a problem anybody help me please? i have down loaded a spread sheet that does what i want but i am having trouble dissecting it and applying it to my project. this is what i need.... sheet1 has my table/list a1 to a10 (ambient temp 25deg,30deg,35deg etc)related to sheet2 cells a5+b5 which are merged as a drop down. sheet1 b1 to b10 with the values (1.04,1,0.91 etc)to enter in sheet2 d5. so what i want is this.... if i select from dropdown eg.. 35degrees i need 0.91 to be entered into sheet2 d5. a little frustrated because i do have an example but as i said i cant figure out how to take it to bits and use it for my needs. if i knew how to post the sheet i would!
many thanks, dave