Creating a custom function with VBA Excel, error #VALUE -

public function copperthermalconductivity(t double, rrr double)      dim p1, p2, p3, p4, p5, p6, p7 double     dim w0, w1, w10 double     dim beta, betar double      beta = 0.634 / rrr     betar = beta / 0.0003      p1 = 0.00000001754     p2 = 2.763     p3 = 1102     p4 = -0.165     p5 = 70     p6 = 1.756     p7 = 0.838 / (betar ^ 0.1661)      w0 = beta / t     w1 = (p1 * (t ^ p2)) / (1 + (p1 * p3 * (t ^ (p2 + p4)) * worksheetfunction.exp(-(p5 / t) ^ p6)) + w0)     w10 = (p7 * w1 * w0) / (w1 + w0)      copperthermalconductivity = (1 / (w0 + w1 + w10))  end function  sub describefunctioncopper()    dim funcname string    dim funcdesc string    dim argdesc(1 2) string     funcname = "copperthermalconductivity"    funcdesc = "returns thermal conductivity in w/m-k"     argdesc(1) = "temperature in kelvin"    argdesc(2) = "residual-resistivity ratio"     application.macrooptions _       macro:=funcname, _       description:=funcdesc, _       argumentdescriptions:=argdesc, _       category:="cryogenics" end sub 

i wrote code create accessible function excel. somehow when use function on excel #value error, idea? don't error when build macro. me please.

this line source of error:

w1 = (p1 * (t ^ p2)) / (1 + (p1 * p3 * (t ^ (p2 + p4)) * worksheetfunction.exp(-(p5 / t) ^ p6)) + w0) 

you cannot use worksheet function exp in vba code. there vba equivalent exp() , should used instead of worksheet function.

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by way, note when declare variables that:

dim p1, p2, p3, p4, p5, p6, p7 double dim w0, w1, w10 double dim beta, betar double 

only p7, w10 , betar declared double, other declared variant. if want declare variables double should that:

dim p1 double, p2 double, p3 double, p4 double, p5 double, p6 double, p7 double dim w0 double, w1 double, w10 double dim beta double, betar double