ListColumn.MinWidthExpression
From Xojo Documentation
Property (As String )
aListColumn.MinWidthExpression = newStringValue
or
StringValue = aListColumn.MinWidthExpression
Supported for all project types and targets.
or
StringValue = aListColumn.MinWidthExpression
Supported for all project types and targets.
The minimum width of the column as a string expression that can include spaces and the percent sign.
Example
The following line sets the minimum width of the first column in a ListBox to 15% of the total width of the ListBox.
Listbox1.Column(0).MinWidthExpression = "15%"