"REM" wrote:
I am trying to get the following to work,
varr = Application.LinEst(ArrayY, Application.Power( _
ArrayX, Array(1, 2)), True, 0)
but I get a type mismatch error.
The arrays are dimensioned as Variant and both redimensioned with:
ReDim ArrayX(1 To NoofVals)

You are trying to mimick the Excel expression
LINEST(ArrayY,ArrayX^{1,2},TRUE,0). You cannot do that directly in VBA.
Try the following (untested):

ReDim ArrayX2(1 to NoofVals, 1 to 2)
for i = 1 to NoofVals: ArrayX2(i,1) = ArrayX(i): Next
for i = 1 to NoofVals: ArrayX2(i,2) = ArrayX(i)^2: Next
varr = Application.LinEst(ArrayY,ArrayX2,True,0)

PS: I think WorksheetFunction.LinEst is preferred. But Application.LinEst
might return errors that WorksheetFunction.LinEst does not(!). At least
that has been my experience with some other WorksheetFunction methods.