As I understand you ... You want to dial a number using  the contents of a
cell on a spreadsheet.

Assuming you have a modem in or attached to the PC, getting it to dial a
number is relatively easy.
If you don't then modems are very very cheap because everyone wants DSL!

I'd use a "good old batch file" and pass it the number as a parameter.
The batch file  would contain the AT commands to go off hook and dial the
number. These would be echoed to the com port the modem is attached to.