Converting decimal LAT/LON to NMEA format

Hi,

I need a program in preferably 'Oshonsoft PIC basic' or 'Excel' or another basic program, that will convert a decimal LAT/LON from 'say' Google maps to the NMEA format.

E,g, ?????.?????
?????.?????

$GPGGA,123456,?????.?????,N,?????.?????,W,1,04,1.80,100.0,M,47.7,M,,*7F?

I'm happy to cut and paste the result into the NMEA sentence.

Is there anyone who can help please?

Camerart.