Change Chart Axis based on Calculation Change

While using a Bar Chart as a Gantt timeline I previously was using cell values to manually update the timeline axis for Min, Max, and MajorUnit - code below where cells C3, C4, and C5 were represented respectively:

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Option Explicit

Private Sub Worksheet_Change(ByVal Target As Range)
Select Case Target.Address
Case "$C$4"
ActiveSheet.ChartObjects("Chart 3").Chart.Axes(xlValue) _
.MaximumScale = Target.Value
Case "$C$3"
ActiveSheet.ChartObjects("Chart 3").Chart.Axes(xlValue) _
.MinimumScale = Target.Value
Case "$C$5"
ActiveSheet.ChartObjects("Chart 3").Chart.Axes(xlValue) _
.MajorUnit = Target.Value
Case Else
End Select
End Sub
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However, I now want to dynamically update the Min, Max, and MajorUnit by way of "calculated" updates. To do so I understand that the method needs to change since the present method is triggering off a cell change on the worksheet that is being entered manually. What would be the simplest way to modify the code based on a calculated change?

Note the calculation is being performed on a separate worksheet that is linked to the same C3, C4, and C5 cells where the Bar Chart is present, and the result is a calendar date - e.g. 1/23/2022.

Thank you in advance for the response!

Version: Office 365 Excel

Right, I assessed the Jon Peltier method of setting up a UDF (function) yet the example only indexes the month - e.g. 2 equals Feb, 3 equals Mar, etc. The Gantt chart is user selectable and can range from months to over several years, so indexing by months alone would not resolve the need. Thanks for the example.

The UDF in the example is called as PT_ScaleChartAxis(SheetName,ChartName,X_or_Y,Primary_or_Secondary,Minimum,Maximum,MajorUnit,MinorUnit).

So if for example the function called is: =PT_ScaleChartAxis("Timeline","Chart 10","X","Primary",C4,C5,C6,C7), where C4 is 1/1/2023, C5 is 12/31/2027, C6 is 365, C7 is 1 results in "Cannot scale a category-type axis". Of course converting the date in to its equivalent number format might work, but then to the user it does not look like a date. Perhaps I'm missing something as the UDF is a direct copy paste and the function appears to be triggering correctly.

For clarification, the chart is rendering the dates on the bar chart grid correctly - e.g. 1/1/2023 format.

You are spot on! Selecting the "Y" axis, the horizontal axis renders the bar chart correctly, even with date values as inputs, or calculated values. Of course I now feel silly and should have caught the bar chart being a rotated column chart making the axis change - Doh!

All hail the Guru :-)