Hmmm, if you wish to be able to add this in a way that you use mixed
separation symbols (as in your example for the "milliseconds" - i'd call it
rather hundreth of seconds) and still have a result displaying hours minutes
seconds and hundreths of seconds, you could use of course (for an addition
for example) a formula such as:
=TEXT(VALUE(LEFT(A1,2))+VALUE(LEFT(A2,2))+((VALUE(MID(A1,4,2))+VALUE(MID(A2,4,2))+((VALUE(MID(A1,7,2))+VALUE(MID(A2,7,2))+((VALUE(RIGHT(A1,2))+VALUE(RIGHT(A2,2)))>99)>59)>59),"#0")&":"&TEXT(MOD(VALUE(MID(A1,4,2))+VALUE(MID(A2,4,2))+((VALUE(MID(A1,7,2))+VALUE(MID(A2,7,2))+((VALUE(RIGHT(A1,2))+VALUE(RIGHT(A2,2)))>99)>59),60),"00")&":"&TEXT(MOD(VALUE(MID(A1,7,2))+VALUE(MID(A2,7,2))+((VALUE(RIGHT(A1,2))+VALUE(RIGHT(A2,2)))>99),60),"00")&":"&TEXT(MOD(VALUE(RIGHT(A1,2))+VALUE(RIGHT(A2,2)),100),"00")
This should work, but I'm sure there's other ways...:-) I'm just too lazy to
think today, and of course you would find a similar approach for
subtraction...
(hope I haven't missed a parenthesis somewhere - no means to test today)
Have fun,
Erny