Sumif, index array ??? Help

[stanster]

Hi
I asked for help on this sheet previously but as with most things this has morphed into something else.
The sheet is almost complete but I need help with the last part
Tab 3 shows a range of materials across the top and a list of diameters down the side. Where the two intersect it gives the number of metres per kg (E.G. material type 304 and diameter 1.62 gives a figure of metres per kg of 61.26)
On the first sheet (sales orders) I can select the material in column E from a drop down list and a diameter in row M from a drop down list (although this list is not complete as yet in line with the m per kg tab)
I need column Q (metres outstanding first draw) to do the following
Look at Column E for the material type, look at Column M for the diameter and check these against the data in the m per KG tab. This will return a figure such as highlighted above. I then need this figure multiplying by Column P

So in short check the material type and diameter entered in Columns E and M, get the corresponding figure from the chart and multiply it by column P and display the outcome in Column Q

Please see attached sheet

Many Thanks

Stanster