When using this dialog box, it is useful sometimes to help users make their
selection, like you can with GetSaveAsFilename, thus:

st = Application.GetSaveAsFilename(Cells(3, 9), "*.mat, *.mat")

But when I try inserting a cell reference into GetOpenFilename it fails,
thus:

st = Application.GetOpenFilename(Cells(3, 9), "*.mat, *.mat")

This fails.

None of my books seems to address this. Has anybody a solution?

Thanks