Hi Rob,

First my formula suggestion: =--TEXT(A1,"0."&REPT("0",A2-1)&"E+000")
In A1 you have your original number, in A2 the count of significant
digits you want.

My UDF:
Function dbl2nsig(d As Double, _
Optional n As Long = 3) _
As String
'Returns string presentation of d with
'n significant digits. PB V0.01
Dim i As Long, j As Long
Dim s As String, sr As String
s = Format(d, "0." & String(n - 1, "0") _
& "E+000")
i = Right(s, 4)
Select Case i
Case Is n - 2
sr = Left(s, 1)
If n 1 Then sr = sr & Mid(s, 3, n - 1)
sr = sr & String(i - n + 1, "0")
Case 0
sr = Left(s, n + 1)
Case Is < 0
sr = "0." & String(-1 - i, "0") & Left(s, 1) _
& Mid(s, 3, n - 1)
Case Else
s = Left(s, 1) & Mid(s, 3, n - 1)
sr = Left(s, i + 1) & "." & _
Right(s, n - i - 1)
End Select
dbl2nsig = sr
End Function

HTH,
Bernd