Removing blank spaces before and after in a cell using VBA

I have a column where users paste a list of numbers (up to 120). It starts at D4 and ends at D123, column D. Sample numbers are: 11111, 11111a, 22222c. Sometimes the users paste numbers and they have spaces either before or after the numbers... Is there a simple code that will solve this for only column D from D4 to D123?

Thanks...