vba - Parsing the Parameters of a Function -

i trying create udf within vba go through function syntax , treat text.

the function :

functiona( param1 , param2 , param3 , param 4 ) 

i trying develop udf pull out value of param based on position input udf function.

getn( functiona , 3 ) = "param3"  getn functiona , 1 ) = "param1"   

here's function far it's off....

it's behaving :

getn( functiona , 0 ) = param2  

here's function:

function getn(sinputstring string, n integer) string      dim sfindwhat string      dim j, finda, findb integer      application.volatile      sfindwhat = ","       finda = 0      j = 0 n          finda = instr(finda + 1, sinputstring, sfindwhat)          findb = instr(finda + 1, sinputstring, sfindwhat)          if findb = 0 findb = instr(finda + 1, sinputstring, ")")          if finda = 0 exit      next      getn = trim(mid(sinputstring, finda + 1, findb - finda - 1))   end function 

thank help

split should work, though correctly handle case of nested functions, preliminary hack first replace commas @ top level safe delimiter (e.g. [[,]]) , splitting on delimiter:

function getparametern(func string, n long) string     dim args variant     dim safeargs string     dim c string     dim long, pdepth long      func = trim(func)     = instr(func, "(")     args = mid(func, + 1)     args = mid(args, 1, len(args) - 1)      = 1 len(args)         c = mid(args, i, 1)         if c = "("             pdepth = pdepth + 1         elseif c = ")"             pdepth = pdepth - 1         elseif c = "," , pdepth = 0             c = "[[,]]"         end if         safeargs = safeargs & c     next     args = split(safeargs, "[[,]]")     getparametern = trim(args(n - 1)) end function 

for example,

sub test()     dim long     = 1 3         debug.print getparametern("f(x,g(x,y,z),z)", i)     next end sub 

produces:

x g(x,y,z) z 

i see no reason make function volatile.