say hour:mins in A1, put B1=INT(A1) (gives hours in B1), C1=(A1-B1)*100
(gives minutes in C1)

Yep, that would do the job for one single entry.
However it would not allow you to add two or more
entries to make a total.

Yes - but I was putting over the principal. I assume that the list of times
is in (say) column A. Set dummy columns B and C to carry the split times -
copy the formula down as far as necessay, add and revert back concatenated
time to bottom of column A (using the contraction descibed earlier).

Keith