AutoFitMergedCellRowHeight

I have created a form for users in the company. They can input text into unlocked cells that have been merged and size for row height.

I received the following suggestion:

Macro by Jim Rech:

Excel does not support automatically adjusting the row height of a merged cell with wrap text set. This procedure serves as a workaround.

Sub AutoFitMergedCellRowHeight()
Dim CurrentRowHeight As Single, MergedCellRgWidth As Single
Dim CurrCell As Range
Dim ActiveCellWidth As Single, PossNewRowHeight As Single
If ActiveCell.MergeCells Then
With ActiveCell.MergeArea
If .Rows.Count = 1 And .WrapText = True Then
Application.ScreenUpdating = False
CurrentRowHeight = .RowHeight
ActiveCellWidth = ActiveCell.ColumnWidth
For Each CurrCell In Selection
MergedCellRgWidth = CurrCell.ColumnWidth + MergedCellRgWidth
Next
.MergeCells = False
.Cells(1).ColumnWidth = MergedCellRgWidth
.EntireRow.AutoFit
PossNewRowHeight = .RowHeight
.Cells(1).ColumnWidth = ActiveCellWidth
.MergeCells = True
.RowHeight = IIf(CurrentRowHeight > PossNewRowHeight, _
CurrentRowHeight, PossNewRowHeight)
End If
End With
End If
End Sub

The script does what it's supposed to but it only does it when I manually run it. My wish is to have the user input their text, hit the enter key and the macro to run automatically without the user even know what is happening. I need the row to autofit when the enter key is pushed.

Anyone have any suggestions?