Can anyone help with the following problem in Excel 97

I would like to enter time as follows and total correctly in hours and
minutes
10:35
10:57
10:20
Total 31:52

However what I have to do is enter_10_shift:_35_etc
and this gives me the following
10:35:
10:57:
10:20:
Total 31:52:

I would rather not have the second set of colons

Any suggestions ?

Thank You