I keep getting the error Access can't find form referred to in macro or vb code when trying to run two macros.

The macros are to set a value in a combo box which is placed on a subform, which in turn is linked to a tab control on the main form I'm using.

Can anyone help with this, the argument I'm using to link to the combo box is:

[Forms]![frmWork_Placement]![frmStudent_Placement]![cmboCourse]

Cheers