Well, if you use sprintf then it should be easy:
Code:
char * colormenu[] = {"red","blue","black"};
char * stylemenu[] = {"4x4","Saloon","Sports"};
char command[100]; // Arbitrary length, make as long as you need it
int colorchoice, stylechoice, loop;
printf("Please enter the color you want\n");
for( loop = 0; loop < sizeof colormenu / sizeof *colormenu; ++loop )
printf("%d.%s\n",loop+1,colormenu[loop]);
scanf("%d",&colorchoice);
printf("Please enter the style you want\n");
for( loop = 0; loop < sizeof stylemenu / sizeof *stylemenu; ++loop )
printf("%d.%s\n",loop+1,stylemenu[loop]);
scanf("%d",&stylechoice);
sprintf(command,"POST MYCAR CP/1.0\r\nCar-Options:#color;%s#style;%s\r\n\r\n ",
colormenu[colorchoice-1],stylemenu[stylechoice-1]);
I skipped the engine related code to cut down on the size for this example. After the code executes, the command character array should contain the formated command string.