How to update Image box controlsource in subform from main form

Question

I have a main form with a subform that loads image records. When I set up the forms I specified the control source for the image box on the subform itself through the properties with the following:

=[Forms]![MainForm]![cmbImageLocation] & [RelativePath] & [ImageFileName]

Where cmbImageLocation is a combobox on the main form with a root directory, and RelativePath is the folder location and ImageFileName is the specific jpeg file.

An example would be:
cmbImageLocation D:\
RelativePath OneDrive\
ImageFileName 001.jpg

The complete concatenated path would be D:\OneDrive\001.jpg

If this code is used in the image box subform control source, the picture loads successfully.
I now need to move the control source specification from the subform to the main form's VBA.

I set up a test textbox in the subform and ran this code in the main form's VBA:

Me.subFormImages!txtTest.ControlSource = "=[Forms]![MainForm]![cmbImageLocation] & [RelativePath] & [ImageFileName]"

I get the proper string D:\OneDrive\001.jpg

If I use the same code to update the image box control source on the subform:

Me.subFormImages!ImgBox.ControlSource = "=[Forms]![MainForm]![cmbImageLocation] & [RelativePath] & [ImageFileName]"

I get

"Run Time error '438': Object doesn't support this property or method".

Answer 1

I worked around this by putting the combo box in the header of the subform, so I didn't need to manipulate the control source through the main form's vba.