Is there a way to calculate the average of a row if some cells are
empty but when calculating the average they should have the value of
the cell to the left?

If the following data is enterered

A B C D E F G

1 3 5 6

For the calculation the cells should use the data

A B C D E F G

1 3 3 3 5 5 6

Also what would the average formula be if you wanted to skip one of the
cells from the average calculation?

Thanks

Tom