Stop Macro Execution From UserForm

On a worksheet I have a command button that displays a ConfigureCatalog form.

Code:
Public StopRequested as Boolean

'Worksheet Command Button will display the Configure Catalog Form
Private Sub CmdConfigure_Click()
CatalogConfigForm.Show vbModeless
End Sub

The ConfigureCatalog userform has two Command Buttons: cmdRebuildCatalog, and cmdStop. RebuildDSWCatalog is a macro that reads and analyzes just over 35,000 records and updates other worksheets. As it runs, it repaints the CatalogConfigForm with a progress message every 100 records. It can run for about 3 minutes. I want to provide a "STOP" button that will allow the user to interrupt the RebuildDSWCatalog macro and return control to the user.

Code:
Private Sub cmdRebuildCatalog_Click()
StopRequested = False
Call RebuildDSWCatalog
End Sub

Private Sub cmdStop_Click()
StopRequested = True
End Sub

While processing the 35,000 records, I want the RebuildDSWCatalog macro to check whether StopRequested has been set to TRUE prior to processing the record. If StopRequested = TRUE, I want to drop out of the macro.

Code:
Public Sub RebuildDSWCatalog()
StopRequested = FALSE
For DSWRecord = DSWStart To DSWCount
If StopRequested = True Then

[Code] ....

Problem is that once the RebuildDSWCatalog macro starts running, the STOP command button never seems to get the focus back. All other input is inhibited until the macro ends.

It just ignores that I'm hitting that STOP button. In fact, the button doesn't visibly respond at all until RebuildDSWCatalog finishes processing all 35,000 records.