How To: Programmatically contract the legend for a raster layer in the ArcMap Table of Contents

Set the ILegendGroup Visible property to False to contract the legend in the Table of Contents (TOC).

Code:
Sub RasterRend()
Dim pDoc As IMxDocument
Set pDoc = ThisDocument
Dim pMap As IMap
Set pMap = pDoc.FocusMap

Dim pLayer As IRasterLayer
Set pLayer = pMap.Layer(0)

Dim pRend As IRasterRenderer
Set pRend = pLayer.Renderer
Dim pLegInfo As ILegendInfo
Set pLegInfo = pRend
Dim pLegGroup As ILegendGroup
Set pLegGroup = pLegInfo.LegendGroup(0)
pLegGroup.Visible = False
pDoc.UpdateContents

End Sub