Try this... if the number that needs altering is cell B2
=Left(B2, 4) & Right(B2, 4)
If you are then comparing that against a number, it may still be a problem because that may be considered a text string. (Of course it might not:D
If it does, I think the following might work...
=(Left(B2, 4) & Right(B2, 4)) * 1
Hope that helps,