Failed to open macos disk image file using virtual box

At the outset I would like to thank you who ever answers this question.

I am getting the following error message while opening a mac os .dmg file using virtual box.(I am trying to run a mac os(mojave) using virtual box on a windows 10 machine with the ultimate goal of creating a ios app using this arrangement)

Failed to open the disk image file ...\Desktop\macOSUpdCombo10.14.2.dmg.

Could not open the medium '..\Desktop\macOSUpdCombo10.14.2.dmg'.

VD: error VERR_VD_DMG_INVALID_HEADER opening image file 'C:..\Desktop\macOSUpdCombo10.14.2.dmg' (VERR_VD_DMG_INVALID_HEADER).

Result Code: E_FAIL (0x80004005) Component: MediumWrap Interface: IMedium {4afe423b-43e0-e9d0-82e8-ceb307940dda} Callee: IVirtualBox {9570b9d5-f1a1-448a-10c5-e12f5285adad} Callee RC: VBOX_E_OBJECT_NOT_FOUND (0x80BB0001)

Can any one please help me in resolving the issue?

I do not think this can be done, the only way/workaround is to buy a machine running Macos.