Hello martinhoos,
Here is sample code.
This code shows width of the slot iFeature.
Option Explicit
Const iFeatureTemplate = "End_mill_straight"
Const iFeatureParameterPrompt = "Enter Diameter"
Sub test()
Dim aCompDef As AssemblyComponentDefinition
Set aCompDef = ThisApplication.ActiveDocument.ComponentDefinition
Dim occ As ComponentOccurrence
For Each occ In aCompDef.Occurrences
If TypeOf occ.Definition Is PartComponentDefinition Then
Dim pCompDef As PartComponentDefinition
Set pCompDef = occ.Definition
Debug.Print pCompDef.Document.DisplayName
Dim iFt As iFeature
For Each iFt In pCompDef.Features.iFeatures
Dim template As String
template = GetBaseName(iFt.iFeatureTemplateDescriptor.LastKnownSourceFileName)
If template = iFeatureTemplate Then
Dim iFtInput As iFeatureInput
For Each iFtInput In iFt.iFeatureDefinition.iFeatureInputs
If TypeOf iFtInput Is iFeatureParameterInput Then
Dim iFtParamInput As iFeatureParameterInput
Set iFtParamInput = iFtInput
If iFtParamInput.Prompt = iFeatureParameterPrompt Then
MsgBox "Part : " & occ.Name & vbCr & _
"Diameter : " & iFtParamInput.Value & " cm"
End If
End If
Next iFtInput
End If
Next iFt
End If
Next occ
End Sub
Function GetBaseName(fullPath As String)
' You need add the "Microsoft Scripting Runtime" to the reference setting.
' If you cannot use this reference with some reason, you must write a code by yourself.
Dim objFSO As New FileSystemObject
GetBaseName = objFSO.GetBaseName(fullPath)
End Function

The model files are attached to this message also.
This macro is stored in the Module1 of Assembly1.iam
If what iFeature is used is known, you can know what part should be placed.
Good luck!
=====
Freeradical
Hideo Yamada