Copy / Past - From a form to a subform

[K]

Good day,

I have a form call frmMain. In this form I have a subform called frmSub.
When the user selects a machine number say 1034 in the frmSub I have a macro
that opens the 1034Soco form to do a calculation displaying a result in a
text box called FTHR.

I have a command button on this form (1034Soco) and onClick I would like to
take the result from the text box called FTHR and transpose it to the subform
How do I, If possible accomplish this?

 

[K]

Transpose it to a field called FTHR in the subform (FrmSub)