sorting a structure

I've created a data file using an array of structures and now I'm trying to create a sort function that will sort the structure member char payTo[15]and print out the file in alphabetical order. I'm trying to use a bubble sort but I can't get it to work. I keep getting an error stating "error C2106: '=' : left operand must be l-value". I don't understand what I'm doing wrong. I've already created a search function that works fine but my sort function has me stumped !
Can anyone look at my code and give me an idea as to what I'm doing wrong ?
Here is what i have:

struct checkBook{
int check;
char payTo[15];
double amt;
char description[15];
}cb[MAX];

main()
//body of main I opened up the file for reading

void search_payTo(void)
{
char payTo[15];
int i, found;

printf("Enter pay to order of to search for: ");
gets(payTo);

found = 0;
for(i=0; i<top; i++)
if(!strcmp(payTo, cb[i].payTo)){
display(i);
found = 1;
printf("\n");
}
if(!found) printf("Not found\n");
}

void sort_payTo(void)
{
int i, j;
char temp[80];

printf("Sorted by Pay to the order of\n");

for(i=1; i<top; i++){
for(j=0; j<top-1; j++){
if(strcmp(cb[j].payTo, cb[j+1].payTo)>0)
{
temp = cb[j].payTo;
cb[j].payTo = cb[j+1].payTo;
cb[j+1] = temp;
}
}
}
}