Sum multiple lookup table across worksheets

[Jkaen]

Hey all, hope you can help me.

I am trying to get a framework contract tracking software sorted and have call in excel to try to obtain data from across various worksheets (circa 60)

The formula I am using for a single worksheet is:
{=INDEX('Sheet 2'!A8:I9,MATCH(A7&C7,'Sheet 2'!D89&'Sheet 2'!E8:E9,0),9)}

(Note this is an array)

What I would like is to sum that value with:
{=INDEX('Sheet 3'!A8:I9,MATCH(A7&C7,'Sheet 3'!D89&'Sheet 3'!E8:E9,0),9)}
{=INDEX('Sheet 4'!A8:I9,MATCH(A7&C7,'Sheet 4'!D89&'Sheet 4'!E8:E9,0),9)}
all the way to
{=INDEX('Sheet 59'!A8:I9,MATCH(A7&C7,'Sheet 59'!D89&'Sheet 59'!E8:E9,0),9)}

Does anybody know an elegant way of doing it?

Thanks
Stephen