Even if you format the column as hh:mm:ss then entering 030528 will
still see this as a date.
You need to have two columns, one to enter the data in the form you
want to and a second one wich you format to automatically display this
as a time.

Suppose you enter the data in A1, use this formula in B1:

=TIME(VALUE(LEFT(TEXT(A1,"000000"),2)),VALUE(MID(T EXT(A1,"000000"),3,2)),VALUE(RIGHT(TEXT(A1,"000000 "),2)))

To get a running total of column B use this in B1 and copy into B2 etc.

=SUM($B$1:B1)

But be careful, this will only display values upto 24 hours and then it
will start with 0 again!

Hans