Way To Return Column String Values

I have made this function that returns the string value for a column based on it's number but it starts getting more complicated after I've been thru the alphabet once and have to return two string values to move across the chart.

PHP

Function colnum_string(ByVal num As Integer) As String    colnum_string = "IV"    If num = 1 Then        colnum_string = "A"    End If    If num = 2 Then        colnum_string = "B"    End If    If num = 3 Then        colnum_string = "C"    End If    If num = 4 Then        colnum_string = "D"    End If    If num = 5 Then        colnum_string = "E"    End If    If num = 6 Then        colnum_string = "F"    End If    If num = 7 Then        colnum_string = "G"    End If    If num = 8 Then        colnum_string = "H"    End If    If num = 9 Then        colnum_string = "I"    End If    If num = 10 Then        colnum_string = "J"    End If    If num = 11 Then        colnum_string = "K"    End If    If num = 12 Then        colnum_string = "L"    End If    If num = 13 Then        colnum_string = "M"    End If    If num = 14 Then        colnum_string = "N"    End If    If num = 15 Then        colnum_string = "O"    End If    If num = 16 Then        colnum_string = "P"    End If    If num = 17 Then        colnum_string = "Q"    End If    If num = 18 Then        colnum_string = "R"    End If    If num = 19 Then        colnum_string = "S"    End If    If num = 20 Then        colnum_string = "T"    End If    If num = 21 Then        colnum_string = "U"    End If    If num = 22 Then        colnum_string = "V"    End If    If num = 23 Then        colnum_string = "W"    End If    If num = 24 Then        colnum_string = "X"    End If    If num = 25 Then        colnum_string = "Y"    End If    If num = 26 Then        colnum_string = "Z"    End IfEnd Function 

Is there a better, more simple way to return the string value for a column from it's number reference?