In Gui how to change vector value?

hy. I would ask help, please

problem: I have 2 m file. The function in the secondary m file (for example: function theta(alfa1) (not same place as the main m file). In that function have vector this s1 =(1;0;0;0).This s1 I would change in Gui ....in edit box I put some number then the the 2nd number of s1 is will change /s1(2) only I need change the 2nd numBer/

please can someone to tell me how to do that....?