Creating a function, needs some help

hey everybody! building arduino based robot, , need collect data 3 ultrasonic sensors(parallax ping specific), , trying measuredistance function work. way able have measuredistance(leftuspin) return value of left sensor, measuredistance(rightuspin) return right, etc.
the problem is, cannot actual function part work. rest of code, when run outside of function, works perfectly.
here important bits of code

quote

//ultrasonic variables
int frontuspin=2; //pin assignment
int frontusdist; //distance var in cm
int leftuspin=3;
int leftusdist;
int rightuspin=4;
int rightusdist;
int usside;
int usdist;
unsigned long pulseduration=0;

void setup()
{

 serial.begin(9600);
}

int measuredistance(usside)
{
 pinmode(usside, output);
 digitalwrite(usside, low);
 delaymicroseconds(5);
 digitalwrite(usside, high);
 delaymicroseconds(5);
 digitalwrite(usside, low);
 pinmode(usside, input);
 pulseduration=pulsein(usside, high);
 pulseduration=pulseduration/2; 
 usdist = int(pulseduration/29);
}

void loop()
{
 serial.print("distance - ");
 serial.print(measuredistance(leftuspin));
 serial.println(" cm");
 delay(500);
}

also, here error output:

code: [select]

ffrobot:10: error: 'usside' not declared in scope
ffrobot:36: error: redefinition of 'int measuredistance'
ffrobot:10: error: 'int measuredistance' defined here
ffrobot.cpp: in function 'void loop()':
ffrobot:67: error: 'measuredistance' cannot used function


any appreciated!

[font=courier new]int measuredistance( int usside )
{[/font]

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