Macro to break-up cell and add formula

I have an issue that has been troubling me for sometime now.

Problem:

I have a gps system connected to an older datalogger that is streaming the data in a very un-user friendly format. It saves the gps location as degrees, and decimal minutes together in one cell, eg. -8032.117179. There are A LOT of data points so this format needs macro to clean it up.

Solution:

I am trying to create a formula that breaks apart -80 (degrees) from the rest and divides 32.117179/60 and then adds the 80 degrees back to the result.

-8032.117179 -------> =-80.5352863

I've tried the following

=-(RIGHT(A2,10))/60+(LEFT(A2,3))

This formula works, but because not all of the data has the same number of significant figures, it only works for a select few.

Rounding does not seem to work.

It would be more then great if someone knew a better way to go about this....

Cheers!!
Simon