This will handle fractional and negative base numbers and negative exponents. It will not handle fractional exponents, but it does handle n^0 :
Code:
Function Pwr($i,Optional $p)

	If Not $p $p=2 EndIf



	If $p<0

		$p=0-$p

		$i=1.0/$i

	EndIf



	$Pwr=1.0



	While $p

		$Pwr=$Pwr*$i

		$p=$p-1

	Loop



EndFunction