Difficulty - No VBA Preferably

I'm trying to pull numeric data from an imported CSV file. The data I
am trying to pull is in a DDD:HH:MM:SS format. I've already written a
function that pulls the data from those fixed fields...

=IF(A2=0,0,SUM(SUM(24*(VALUE(LEFT(A2,3))))+(VALUE( MID(A2,5,2)))+(SUM(VALUE(MID(A2,8,2)))/60)))

What the function does is convert the DDD:HH:MM into a decimal form
which is easier to read and to perform additional functions with.

Here's the problem....most of the data comes into the exported csv file
like this...

000:11:05:46 ---- function ---- 11.08 CORRECT!

But on occasion, it exports like this....

00:11:05:46 ---- 0.05 ---- NOT CORRECT!

The problem with my function is that is the date field is shortened, it
screws up the answer completely. What I need is a way to pull the
numerical data out of the field by using the ":" instead of just using
fixed characters. I've obviously rewritten the formula in those
specific cases, but I was looking for something more elegant if it
exists. Also, I really don't want to use "Text to Columns" since this
worksheet will eventually be used by a bunch of people and I'm trying
to make it as user friendly as possible.

Thanks,
Brian