I was not able to come up with a Format Pattern that worked, however, the following simple script works
For Each Row(
If( Contains( :column 1, ":" ),
:column 1 = Char(
Num( Word( 1, :column 1, ":" ) ) * 60 + Num( Word( 2, :column 1, ":" ) )
)
)
);
:column 1 << data type( numeric ) << modeling type( continuous );
Jim