Win 10, Office 365
All I did was use Option Explicit and Dim z1 as a Double
Possibly (bold, underlined) not Dim-ing it on a Mac it'd be a variant and that might cause an issue
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Option Explicit Sub a_test_digammad() Dim z1 As Double For z1 = 1 To 4.01 Step 0.1 Debug.Print z1, diGammad(z1) Next z1 End Sub Function diGammad(x) diGammad = x End Function