Positioning cursor in subform

[Kevin Sprinkel]

I have the following forms and controls:

Main Form frmSteelTakeoff
txtJobNumber
txtJobDescription
cmdChangeReference
cmdChangeDefaultSteelType
cmdExporttoExcel
cmdPreviewReport

Subform sbfSteelTakeoffDetail
txtReference
txtSteelType DLookup using txtSteelTypeID
txtSteelTypeID (invisible)
cboSteelSize
txtLength
...several others to calculate total SF and LB

I recently changed txtSteelType to a text box rather than
a combo box because cboSteelSize gets its Row Source based
on the steel type. When the type was changed, data not
matching the Row Source "disappeared".

When the user wants to change the default steel type, he
presses a command button on the main form. This opens a
dialog form consisting of a single combo box. Once the
value is selected, the new Default Value is written to the
subform txtSteelTypeID control, and the dialog closes.

My question is: since I pressed a button on the main
form, how can I return the user to the subform record on
which he was working?

TIA
Kevin Sprinkel