This is my leading script.

KixGolf score = 276

Single use only. +5 stroke for multi-use. remove the ";" in front of "Dim"
code:
Function BaseConverter($v,$d,$e)
	;Dim $B
	$m = '123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'
	$ = CDBL(1)
	$i = len($v)
	Do
		$x = instr($m,substr($v,$i,1))
		$j = $ * $x + $j
		$ = $ * $d
		$i = $i - 1
	Until $i = 0

	$ = $ / $
	do
		$ = $ * $e
	Until $j < $ * $e
	Do
		$z = int($j / $)
		$B = $B + substr($m,$z,1)
		if $j >= $
			$j = $j - $ * $z
		endif
		$ = $ / $e
	Until $<1
	$BaseConverter=$B
Endfunction
;!
break on
BaseConverter("44680832201",10,36) ?
;BaseConverter("78","11","13") ?
;BaseConverter("2","3","2") ?
;BaseConverter("23423","5","12") ?
;BaseConverter("BrianTX","36","10") ?
;BaseConverter("64","8","2")
;BaseConverter('Kixtart',36,10) ?
;BaseConverter('52',10,2) ?
;BaseConverter('52','10','2') ?
This is my runner up
KixGolf score = 278

Same disclaimer on the "Dim" +5 strokes for multi-use.
code:
Function BaseConverter($v,$d,$e)
	;Dim $B
	$ = CDBL(1)
	$i = len($v)
	Do
		$x = Asc(ucase(substr($v,$i,1))) - 48
		If $x > 9
			$x = $x - 7
		endif
		$j = $ * $x + $j
		$ = $ * $d
		$i = $i - 1
	Until $i = 0

	$ = $ / $
	do
		$ = $ * $e
	Until $j < $ * $e
	Do
		$z = int($j / $)
		$x = $z + 48
		if $x > 57
			$x = $x + 7
		endif
		$B = $B + chr($x)
		if $j >= $
			$j = $j - $ * $z
		endif
		$ = $ / $e
	Until $<1
	$BaseConverter=$B
Endfunction
;!
break on
BaseConverter("44680832201",10,36) ?
;BaseConverter('Kixtart',36,10) ?
;BaseConverter('52',10,2) ?
;BaseConverter('52','10','2') ?
;BaseConverter("78","11","13") ?
;BaseConverter("2","3","2") ?
;BaseConverter("23423","5","12") ?
;BaseConverter("BrianTX","36","10") ?
;BaseConverter("64","8","2") ?
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