How do I enter income earned in different provinces in box 120 of my T5013? Need to allocate income for four different provinces.

I am a partner in a national law firm, with offices in four provinces, including Quebec.  My T5013 allocates my portion of the partnership's income to each of those four provinces.  The TurboTax program only allows me to enter one amount in box 120, and does not allow me to stipulate the province to which that income should be allocated.  Any suggestions?