Option Explicit

Public Function TemperatureConv()

Dim Celsius As Double

If CheckNumericCell(Sheet1.Cells(1, 2)) = True Then
    Celsius = Sheet1.Cells(1, 2)
Else
    MsgBox "Please enter valid data for Temperature in Celsius"
    Exit Function
End If

Sheet1.Cells(3, 2) = (9 / 5 * Celsius) + 32

End Function